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authorPetr Mladek <pmladek@suse.cz>2014-04-03 14:48:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-03 16:21:07 -0700
commit39b25109b400ea397e64c417d8b965a53e2ee0f0 (patch)
tree228213814478431701cd6bb53460c6da890b6797 /kernel
parente8c42d36ab86cf45f88c3a0e344233b1032fbf3d (diff)
downloadlinux-39b25109b400ea397e64c417d8b965a53e2ee0f0.tar.gz
printk: use also the last bytes in the ring buffer
It seems that we have newer used the last byte in the ring buffer. In fact, we have newer used the last 4 bytes because of padding. First problem is in the check for free space. The exact number of free bytes is enough to store the length of data. Second problem is in the check where the ring buffer is rotated. The left side counts the first unused index. It is unused, so it might be the same as the size of the buffer. Note that the first problem has to be fixed together with the second one. Otherwise, the buffer is rotated even when there is enough space on the end of the buffer. Then the beginning of the buffer is rewritten and valid entries get corrupted. Signed-off-by: Petr Mladek <pmladek@suse.cz> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jan Kara <jack@suse.cz> Cc: Michal Hocko <mhocko@suse.cz> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/printk/printk.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 012f3e40671..b3a1790f9e0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -319,7 +319,7 @@ static void log_store(int facility, int level,
else
free = log_first_idx - log_next_idx;
- if (free > size + sizeof(struct printk_log))
+ if (free >= size + sizeof(struct printk_log))
break;
/* drop old messages until we have enough contiuous space */
@@ -327,7 +327,7 @@ static void log_store(int facility, int level,
log_first_seq++;
}
- if (log_next_idx + size + sizeof(struct printk_log) >= log_buf_len) {
+ if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
/*
* This message + an additional empty header does not fit
* at the end of the buffer. Add an empty header with len == 0