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bpf:bpf_seq_printf(): handle potentially unsafe format string better 

User the proper helper for kernel or userspace addresses based on
TASK_SIZE instead of the dangerous strncpy_from_unsafe function.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrew Morton 2020-06-08 21:34:37 -07:00 committed by Linus Torvalds
parent aec6ce5913
commit 19c8d8ac63
1 changed files with 5 additions and 3 deletions
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8
kernel/trace/bpf_trace.c
View File

@ -588,15 +588,17 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
} }
if (fmt[i] == 's') { if (fmt[i] == 's') {
void *unsafe_ptr;
/* try our best to copy */ /* try our best to copy */
if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) { if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
err = -E2BIG; err = -E2BIG;
goto out; goto out;
} }
err = strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt], unsafe_ptr = (void *)(long)args[fmt_cnt];
(void *) (long) args[fmt_cnt], err = strncpy_from_kernel_nofault(bufs->buf[memcpy_cnt],
MAX_SEQ_PRINTF_STR_LEN); unsafe_ptr, MAX_SEQ_PRINTF_STR_LEN);
if (err < 0) if (err < 0)
bufs->buf[memcpy_cnt][0] = '\0'; bufs->buf[memcpy_cnt][0] = '\0';
params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt]; params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt];