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printk: fix possible reuse of va_list variable

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I noticed that there is a possibility that printk_safe_log_store() causes
kernel oops because "args" parameter is passed to vsnprintf() again when
atomic_cmpxchg() detected that we raced. Fix this by using va_copy().

Link: http://lkml.kernel.org/r/[email protected]
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Tetsuo Handa <[email protected]>
Fixes: 42a0bb3f71 ("printk/nmi: generic solution for safe printk in NMI")
Cc: 4.7+ <[email protected]> # v4.7+
Reviewed-by: Sergey Senozhatsky <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
This commit is contained in:
Tetsuo Handa 2018-05-11 19:54:19 +09:00 • committed by Petr Mladek
commit 988a35f8da
1 changed files with 4 additions and 1 deletions
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5
kernel/printk/printk_safe.c
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@ -82,6 +82,7 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s,
{
int add;
size_t len;
va_list ap;
again:
len = atomic_read(&s->len);
@ -100,7 +101,9 @@ again:
if (!len)
smp_rmb();
add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args);
va_copy(ap, args);
add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, ap);
va_end(ap);
if (!add)
return 0;