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authorPatrick Palka <patrick@parcs.ath.cx>2014-09-09 14:50:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-09-10 15:42:12 -0700
commit000a7d66ec30898f46869be01ab8205b056385d0 (patch)
treec0d3fbb734cbc03633832c6f24439fe7c9f9c47d
parent0a313a998adbae19c1309f80a3ad79107fff7c4e (diff)
kernel/printk/printk.c: fix faulty logic in the case of recursive printk
We shouldn't set text_len in the code path that detects printk recursion because text_len corresponds to the length of the string inside textbuf. A few lines down from the line text_len = strlen(recursion_msg); is the line text_len += vscnprintf(text + text_len, ...); So if printk detects recursion, it sets text_len to 29 (the length of recursion_msg) and logs an error. Then the message supplied by the caller of printk is stored inside textbuf but offset by 29 bytes. This means that the output of the recursive call to printk will contain 29 bytes of garbage in front of it. This defect is caused by commit 458df9fd4815 ("printk: remove separate printk_sched buffers and use printk buf instead") which turned the line text_len = vscnprintf(text, ...); into text_len += vscnprintf(text + text_len, ...); To fix this, this patch avoids setting text_len when logging the printk recursion error. This patch also marks unlikely() the branch leading up to this code. Fixes: 458df9fd4815b478 ("printk: remove separate printk_sched buffers and use printk buf instead") Signed-off-by: Patrick Palka <patrick@parcs.ath.cx> Reviewed-by: Petr Mladek <pmladek@suse.cz> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/printk/printk.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e04c455a0e38..1ce770687ea8 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1665,15 +1665,15 @@ asmlinkage int vprintk_emit(int facility, int level,
raw_spin_lock(&logbuf_lock);
logbuf_cpu = this_cpu;
- if (recursion_bug) {
+ if (unlikely(recursion_bug)) {
static const char recursion_msg[] =
"BUG: recent printk recursion!";
recursion_bug = 0;
- text_len = strlen(recursion_msg);
/* emit KERN_CRIT message */
printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
- NULL, 0, recursion_msg, text_len);
+ NULL, 0, recursion_msg,
+ strlen(recursion_msg));
}
/*