diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index 45e66a60a816..c47f381d0c00 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -198,6 +198,15 @@ The glob (~) accepts a wild card character (\*,?) and character classes prev_comm ~ "*sh*" prev_comm ~ "ba*sh" +If the field is a pointer that points into user space (for example +"filename" from sys_enter_openat), then you have to append ".ustring" to the +field name:: + + filename.ustring ~ "password" + +As the kernel will have to know how to retrieve the memory that the pointer +is at from user space. + 5.2 Setting filters ------------------- diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 2e9ef64e9ee9..b458a9afa2c0 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -665,6 +665,23 @@ struct ustring_buffer { static __percpu struct ustring_buffer *ustring_per_cpu; static __always_inline char *test_string(char *str) +{ + struct ustring_buffer *ubuf; + char *kstr; + + if (!ustring_per_cpu) + return NULL; + + ubuf = this_cpu_ptr(ustring_per_cpu); + kstr = ubuf->buffer; + + /* For safety, do not trust the string pointer */ + if (!strncpy_from_kernel_nofault(kstr, str, USTRING_BUF_SIZE)) + return NULL; + return kstr; +} + +static __always_inline char *test_ustring(char *str) { struct ustring_buffer *ubuf; char __user *ustr; @@ -676,23 +693,11 @@ static __always_inline char *test_string(char *str) ubuf = this_cpu_ptr(ustring_per_cpu); kstr = ubuf->buffer; - /* - * We use TASK_SIZE to denote user or kernel space, but this will - * not work for all architectures. If it picks the wrong one, it may - * just fail the filter (but will not bug). - * - * TODO: Have a way to properly denote which one this is for. - */ - if (likely((unsigned long)str >= TASK_SIZE)) { - /* For safety, do not trust the string pointer */ - if (!strncpy_from_kernel_nofault(kstr, str, USTRING_BUF_SIZE)) - return NULL; - } else { - /* user space address? */ - ustr = (char __user *)str; - if (!strncpy_from_user_nofault(kstr, ustr, USTRING_BUF_SIZE)) - return NULL; - } + /* user space address? */ + ustr = (char __user *)str; + if (!strncpy_from_user_nofault(kstr, ustr, USTRING_BUF_SIZE)) + return NULL; + return kstr; } @@ -709,18 +714,11 @@ static int filter_pred_string(struct filter_pred *pred, void *event) return match; } -/* Filter predicate for char * pointers */ -static int filter_pred_pchar(struct filter_pred *pred, void *event) +static __always_inline int filter_pchar(struct filter_pred *pred, char *str) { - char **addr = (char **)(event + pred->offset); - char *str; int cmp, match; int len; - str = test_string(*addr); - if (!str) - return 0; - len = strlen(str) + 1; /* including tailing '\0' */ cmp = pred->regex.match(str, &pred->regex, len); @@ -728,6 +726,31 @@ static int filter_pred_pchar(struct filter_pred *pred, void *event) return match; } +/* Filter predicate for char * pointers */ +static int filter_pred_pchar(struct filter_pred *pred, void *event) +{ + char **addr = (char **)(event + pred->offset); + char *str; + + str = test_string(*addr); + if (!str) + return 0; + + return filter_pchar(pred, str); +} + +/* Filter predicate for char * pointers in user space*/ +static int filter_pred_pchar_user(struct filter_pred *pred, void *event) +{ + char **addr = (char **)(event + pred->offset); + char *str; + + str = test_ustring(*addr); + if (!str) + return 0; + + return filter_pchar(pred, str); +} /* * Filter predicate for dynamic sized arrays of characters. @@ -1232,6 +1255,7 @@ static int parse_pred(const char *str, void *data, struct filter_pred *pred = NULL; char num_buf[24]; /* Big enough to hold an address */ char *field_name; + bool ustring = false; char q; u64 val; int len; @@ -1266,6 +1290,12 @@ static int parse_pred(const char *str, void *data, return -EINVAL; } + /* See if the field is a user space string */ + if ((len = str_has_prefix(str + i, ".ustring"))) { + ustring = true; + i += len; + } + while (isspace(str[i])) i++; @@ -1405,7 +1435,10 @@ static int parse_pred(const char *str, void *data, goto err_mem; } - pred->fn = filter_pred_pchar; + if (ustring) + pred->fn = filter_pred_pchar_user; + else + pred->fn = filter_pred_pchar; } /* go past the last quote */ i++;