staging: android: logger: Allow a UID to read it's own log entries
Modify the kernel logger to record the UID associated with the log entries. Always allow the same UID which generated a log message to read the log message. Allow anyone in the logs group, or anyone with CAP_SYSLOG, to read all log entries. In addition, allow the client to upgrade log formats, so they can get additional information from the kernel. Cc: Android Kernel Team <kernel-team@android.com> Cc: Nick Kralevich <nnk@google.com> Signed-off-by: Nick Kralevich <nnk@google.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nick Kralevich
Greg Kroah-Hartman
parent
99150f6a1a
commit
0441bcf4db
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@ -68,6 +68,8 @@ static LIST_HEAD(log_list);
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* @log: The associated log
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* @list: The associated entry in @logger_log's list
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* @r_off: The current read head offset.
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* @r_all: Reader can read all entries
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* @r_ver: Reader ABI version
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*
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* This object lives from open to release, so we don't need additional
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* reference counting. The structure is protected by log->mutex.
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@ -76,6 +78,8 @@ struct logger_reader {
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struct logger_log *log;
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struct list_head list;
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size_t r_off;
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bool r_all;
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int r_ver;
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};
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/* logger_offset - returns index 'n' into the log via (optimized) modulus */
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@ -109,8 +113,29 @@ static inline struct logger_log *file_get_log(struct file *file)
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}
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/*
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* get_entry_len - Grabs the length of the payload of the next entry starting
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* from 'off'.
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* get_entry_header - returns a pointer to the logger_entry header within
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* 'log' starting at offset 'off'. A temporary logger_entry 'scratch' must
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* be provided. Typically the return value will be a pointer within
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* 'logger->buf'. However, a pointer to 'scratch' may be returned if
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* the log entry spans the end and beginning of the circular buffer.
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*/
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static struct logger_entry *get_entry_header(struct logger_log *log,
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size_t off, struct logger_entry *scratch)
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{
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size_t len = min(sizeof(struct logger_entry), log->size - off);
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if (len != sizeof(struct logger_entry)) {
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memcpy(((void *) scratch), log->buffer + off, len);
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memcpy(((void *) scratch) + len, log->buffer,
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sizeof(struct logger_entry) - len);
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return scratch;
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}
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return (struct logger_entry *) (log->buffer + off);
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}
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/*
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* get_entry_msg_len - Grabs the length of the message of the entry
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* starting from from 'off'.
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*
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* An entry length is 2 bytes (16 bits) in host endian order.
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* In the log, the length does not include the size of the log entry structure.
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@ -118,20 +143,45 @@ static inline struct logger_log *file_get_log(struct file *file)
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*
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* Caller needs to hold log->mutex.
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*/
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static __u32 get_entry_len(struct logger_log *log, size_t off)
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static __u32 get_entry_msg_len(struct logger_log *log, size_t off)
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{
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__u16 val;
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struct logger_entry scratch;
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struct logger_entry *entry;
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/* copy 2 bytes from buffer, in memcpy order, */
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/* handling possible wrap at end of buffer */
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entry = get_entry_header(log, off, &scratch);
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return entry->len;
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}
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((__u8 *)&val)[0] = log->buffer[off];
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if (likely(off+1 < log->size))
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((__u8 *)&val)[1] = log->buffer[off+1];
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static size_t get_user_hdr_len(int ver)
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{
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if (ver < 2)
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return sizeof(struct user_logger_entry_compat);
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else
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((__u8 *)&val)[1] = log->buffer[0];
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return sizeof(struct logger_entry);
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}
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return sizeof(struct logger_entry) + val;
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static ssize_t copy_header_to_user(int ver, struct logger_entry *entry,
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char __user *buf)
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{
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void *hdr;
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size_t hdr_len;
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struct user_logger_entry_compat v1;
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if (ver < 2) {
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v1.len = entry->len;
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v1.__pad = 0;
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v1.pid = entry->pid;
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v1.tid = entry->tid;
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v1.sec = entry->sec;
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v1.nsec = entry->nsec;
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hdr = &v1;
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hdr_len = sizeof(struct user_logger_entry_compat);
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} else {
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hdr = entry;
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hdr_len = sizeof(struct logger_entry);
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}
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return copy_to_user(buf, hdr, hdr_len);
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}
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/*
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@ -145,15 +195,31 @@ static ssize_t do_read_log_to_user(struct logger_log *log,
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char __user *buf,
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size_t count)
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{
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struct logger_entry scratch;
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struct logger_entry *entry;
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size_t len;
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size_t msg_start;
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/*
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* We read from the log in two disjoint operations. First, we read from
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* the current read head offset up to 'count' bytes or to the end of
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* First, copy the header to userspace, using the version of
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* the header requested
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*/
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entry = get_entry_header(log, reader->r_off, &scratch);
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if (copy_header_to_user(reader->r_ver, entry, buf))
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return -EFAULT;
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count -= get_user_hdr_len(reader->r_ver);
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buf += get_user_hdr_len(reader->r_ver);
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msg_start = logger_offset(log,
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reader->r_off + sizeof(struct logger_entry));
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/*
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* We read from the msg in two disjoint operations. First, we read from
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* the current msg head offset up to 'count' bytes or to the end of
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* the log, whichever comes first.
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*/
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len = min(count, log->size - reader->r_off);
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if (copy_to_user(buf, log->buffer + reader->r_off, len))
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len = min(count, log->size - msg_start);
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if (copy_to_user(buf, log->buffer + msg_start, len))
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return -EFAULT;
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/*
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@ -164,9 +230,34 @@ static ssize_t do_read_log_to_user(struct logger_log *log,
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if (copy_to_user(buf + len, log->buffer, count - len))
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return -EFAULT;
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reader->r_off = logger_offset(log, reader->r_off + count);
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reader->r_off = logger_offset(log, reader->r_off +
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sizeof(struct logger_entry) + count);
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return count;
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return count + get_user_hdr_len(reader->r_ver);
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}
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/*
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* get_next_entry_by_uid - Starting at 'off', returns an offset into
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* 'log->buffer' which contains the first entry readable by 'euid'
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*/
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static size_t get_next_entry_by_uid(struct logger_log *log,
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size_t off, uid_t euid)
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{
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while (off != log->w_off) {
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struct logger_entry *entry;
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struct logger_entry scratch;
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size_t next_len;
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entry = get_entry_header(log, off, &scratch);
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if (entry->euid == euid)
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return off;
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next_len = sizeof(struct logger_entry) + entry->len;
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off = logger_offset(log, off + next_len);
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}
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return off;
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}
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/*
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@ -178,7 +269,7 @@ static ssize_t do_read_log_to_user(struct logger_log *log,
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* - If there are no log entries to read, blocks until log is written to
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* - Atomically reads exactly one log entry
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*
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* Optimal read size is LOGGER_ENTRY_MAX_LEN. Will set errno to EINVAL if read
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* Will set errno to EINVAL if read
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* buffer is insufficient to hold next entry.
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*/
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static ssize_t logger_read(struct file *file, char __user *buf,
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@ -219,6 +310,10 @@ start:
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mutex_lock(&log->mutex);
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if (!reader->r_all)
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reader->r_off = get_next_entry_by_uid(log,
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reader->r_off, current_euid());
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/* is there still something to read or did we race? */
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if (unlikely(log->w_off == reader->r_off)) {
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mutex_unlock(&log->mutex);
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@ -226,7 +321,8 @@ start:
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}
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/* get the size of the next entry */
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ret = get_entry_len(log, reader->r_off);
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ret = get_user_hdr_len(reader->r_ver) +
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get_entry_msg_len(log, reader->r_off);
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if (count < ret) {
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ret = -EINVAL;
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goto out;
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@ -252,7 +348,8 @@ static size_t get_next_entry(struct logger_log *log, size_t off, size_t len)
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size_t count = 0;
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do {
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size_t nr = get_entry_len(log, off);
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size_t nr = sizeof(struct logger_entry) +
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get_entry_msg_len(log, off);
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off = logger_offset(log, off + nr);
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count += nr;
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} while (count < len);
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@ -382,7 +479,9 @@ static ssize_t logger_aio_write(struct kiocb *iocb, const struct iovec *iov,
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header.tid = current->pid;
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header.sec = now.tv_sec;
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header.nsec = now.tv_nsec;
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header.euid = current_euid();
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header.len = min_t(size_t, iocb->ki_left, LOGGER_ENTRY_MAX_PAYLOAD);
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header.hdr_size = sizeof(struct logger_entry);
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/* null writes succeed, return zero */
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if (unlikely(!header.len))
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@ -463,6 +562,10 @@ static int logger_open(struct inode *inode, struct file *file)
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return -ENOMEM;
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reader->log = log;
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reader->r_ver = 1;
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reader->r_all = in_egroup_p(inode->i_gid) ||
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capable(CAP_SYSLOG);
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INIT_LIST_HEAD(&reader->list);
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mutex_lock(&log->mutex);
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@ -522,6 +625,10 @@ static unsigned int logger_poll(struct file *file, poll_table *wait)
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poll_wait(file, &log->wq, wait);
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mutex_lock(&log->mutex);
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if (!reader->r_all)
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reader->r_off = get_next_entry_by_uid(log,
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reader->r_off, current_euid());
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if (log->w_off != reader->r_off)
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ret |= POLLIN | POLLRDNORM;
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mutex_unlock(&log->mutex);
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@ -529,11 +636,25 @@ static unsigned int logger_poll(struct file *file, poll_table *wait)
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return ret;
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}
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static long logger_set_version(struct logger_reader *reader, void __user *arg)
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{
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int version;
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if (copy_from_user(&version, arg, sizeof(int)))
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return -EFAULT;
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if ((version < 1) || (version > 2))
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return -EINVAL;
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reader->r_ver = version;
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return 0;
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}
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static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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{
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struct logger_log *log = file_get_log(file);
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struct logger_reader *reader;
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long ret = -ENOTTY;
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long ret = -EINVAL;
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void __user *argp = (void __user *) arg;
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mutex_lock(&log->mutex);
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@ -558,8 +679,14 @@ static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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break;
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}
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reader = file->private_data;
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if (!reader->r_all)
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reader->r_off = get_next_entry_by_uid(log,
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reader->r_off, current_euid());
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if (log->w_off != reader->r_off)
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ret = get_entry_len(log, reader->r_off);
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ret = get_user_hdr_len(reader->r_ver) +
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get_entry_msg_len(log, reader->r_off);
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else
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ret = 0;
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break;
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@ -573,6 +700,22 @@ static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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log->head = log->w_off;
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ret = 0;
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break;
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case LOGGER_GET_VERSION:
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if (!(file->f_mode & FMODE_READ)) {
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ret = -EBADF;
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break;
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}
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reader = file->private_data;
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ret = reader->r_ver;
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break;
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case LOGGER_SET_VERSION:
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if (!(file->f_mode & FMODE_READ)) {
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ret = -EBADF;
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break;
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}
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reader = file->private_data;
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ret = logger_set_version(reader, argp);
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break;
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}
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mutex_unlock(&log->mutex);
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@ -592,8 +735,8 @@ static const struct file_operations logger_fops = {
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};
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/*
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* Log size must be a power of two, greater than LOGGER_ENTRY_MAX_LEN,
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* and less than LONG_MAX minus LOGGER_ENTRY_MAX_LEN.
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* Log size must must be a power of two, and greater than
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* (LOGGER_ENTRY_MAX_PAYLOAD + sizeof(struct logger_entry)).
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*/
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static int __init create_log(char *log_name, int size)
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{
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@ -21,7 +21,7 @@
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#include <linux/ioctl.h>
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/**
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* struct logger_entry - defines a single entry that is given to a logger
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* struct user_logger_entry_compat - defines a single entry that is given to a logger
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* @len: The length of the payload
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* @__pad: Two bytes of padding that appear to be required
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* @pid: The generating process' process ID
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@ -29,8 +29,12 @@
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* @sec: The number of seconds that have elapsed since the Epoch
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* @nsec: The number of nanoseconds that have elapsed since @sec
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* @msg: The message that is to be logged
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*
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* The userspace structure for version 1 of the logger_entry ABI.
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* This structure is returned to userspace unless the caller requests
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* an upgrade to a newer ABI version.
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*/
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struct logger_entry {
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struct user_logger_entry_compat {
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__u16 len;
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__u16 __pad;
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__s32 pid;
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@ -40,14 +44,38 @@ struct logger_entry {
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char msg[0];
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};
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/**
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* struct logger_entry - defines a single entry that is given to a logger
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* @len: The length of the payload
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* @hdr_size: sizeof(struct logger_entry_v2)
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* @pid: The generating process' process ID
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* @tid: The generating process' thread ID
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* @sec: The number of seconds that have elapsed since the Epoch
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* @nsec: The number of nanoseconds that have elapsed since @sec
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* @euid: Effective UID of logger
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* @msg: The message that is to be logged
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*
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* The structure for version 2 of the logger_entry ABI.
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* This structure is returned to userspace if ioctl(LOGGER_SET_VERSION)
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* is called with version >= 2
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*/
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struct logger_entry {
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__u16 len;
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__u16 hdr_size;
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__s32 pid;
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__s32 tid;
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__s32 sec;
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__s32 nsec;
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uid_t euid;
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char msg[0];
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};
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#define LOGGER_LOG_RADIO "log_radio" /* radio-related messages */
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#define LOGGER_LOG_EVENTS "log_events" /* system/hardware events */
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#define LOGGER_LOG_SYSTEM "log_system" /* system/framework messages */
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#define LOGGER_LOG_MAIN "log_main" /* everything else */
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#define LOGGER_ENTRY_MAX_LEN (4*1024)
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#define LOGGER_ENTRY_MAX_PAYLOAD \
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(LOGGER_ENTRY_MAX_LEN - sizeof(struct logger_entry))
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#define LOGGER_ENTRY_MAX_PAYLOAD 4076
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#define __LOGGERIO 0xAE
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@ -55,5 +83,7 @@ struct logger_entry {
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#define LOGGER_GET_LOG_LEN _IO(__LOGGERIO, 2) /* used log len */
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#define LOGGER_GET_NEXT_ENTRY_LEN _IO(__LOGGERIO, 3) /* next entry len */
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#define LOGGER_FLUSH_LOG _IO(__LOGGERIO, 4) /* flush log */
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#define LOGGER_GET_VERSION _IO(__LOGGERIO, 5) /* abi version */
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#define LOGGER_SET_VERSION _IO(__LOGGERIO, 6) /* abi version */
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#endif /* _LINUX_LOGGER_H */
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