Subject: + printk-split-code-for-making-free-space-in-the-log-buffer.patch added to -mm tree
To: pmladek@xxxxxxx,jack@xxxxxxx,jkosina@xxxxxxx,kay@xxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 18 Apr 2014 12:03:47 -0700
The patch titled
Subject: printk: split code for making free space in the log buffer
has been added to the -mm tree. Its filename is
printk-split-code-for-making-free-space-in-the-log-buffer.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/printk-split-code-for-making-free-space-in-the-log-buffer.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/printk-split-code-for-making-free-space-in-the-log-buffer.patch
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------------------------------------------------------
From: Petr Mladek <pmladek@xxxxxxx>
Subject: printk: split code for making free space in the log buffer
The check for free space in the log buffer always passes when "first_seq"
and "next_seq" are equal. In theory, it might cause writing outside of
the log buffer.
Fortunately, the current usage looks safe because the used "text" and
"dict" buffers are quite limited. See the second patch for more details.
Anyway, it is better to be on the safe side and add a check. An easy
solution is done in the 2nd patch and it is improved in the 4th patch.
5th patch fixes the computation of the printed message length.
1st and 3rd patches just do some code refactoring to make the other
patches easier.
This patch (of 5):
There will be needed some fixes in the check for free space. They will be
easier if the code is moved outside of the quite long log_store()
function.
This patch does not change the existing behavior.
Signed-off-by: Petr Mladek <pmladek@xxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Kay Sievers <kay@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/printk/printk.c | 44 +++++++++++++++++++++++++--------------
1 file changed, 29 insertions(+), 15 deletions(-)
diff -puN kernel/printk/printk.c~printk-split-code-for-making-free-space-in-the-log-buffer kernel/printk/printk.c
--- a/kernel/printk/printk.c~printk-split-code-for-making-free-space-in-the-log-buffer
+++ a/kernel/printk/printk.c
@@ -297,6 +297,34 @@ static u32 log_next(u32 idx)
return idx + msg->len;
}
+/* check whether there is enough free space for the given message */
+static int logbuf_has_space(u32 msg_size)
+{
+ u32 free;
+
+ if (log_next_idx > log_first_idx)
+ free = max(log_buf_len - log_next_idx, log_first_idx);
+ else
+ free = log_first_idx - log_next_idx;
+
+ /*
+ * We need space also for an empty header that signalizes wrapping
+ * of the buffer.
+ */
+ return free >= msg_size + sizeof(struct printk_log);
+}
+
+static void log_make_free_space(u32 msg_size)
+{
+ while (log_first_seq < log_next_seq) {
+ if (logbuf_has_space(msg_size))
+ return;
+ /* drop old messages until we have enough continuous space */
+ log_first_idx = log_next(log_first_idx);
+ log_first_seq++;
+ }
+}
+
/* insert record into the buffer, discard old ones, update heads */
static void log_store(int facility, int level,
enum log_flags flags, u64 ts_nsec,
@@ -311,21 +339,7 @@ static void log_store(int facility, int
pad_len = (-size) & (LOG_ALIGN - 1);
size += pad_len;
- while (log_first_seq < log_next_seq) {
- u32 free;
-
- if (log_next_idx > log_first_idx)
- free = max(log_buf_len - log_next_idx, log_first_idx);
- else
- free = log_first_idx - log_next_idx;
-
- if (free >= size + sizeof(struct printk_log))
- break;
-
- /* drop old messages until we have enough contiuous space */
- log_first_idx = log_next(log_first_idx);
- log_first_seq++;
- }
+ log_make_free_space(size);
if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
/*
_
Patches currently in -mm which might be from pmladek@xxxxxxx are
printk-split-code-for-making-free-space-in-the-log-buffer.patch
printk-ignore-too-long-messages.patch
printk-split-message-size-computation.patch
printk-shrink-too-long-messages.patch
printk-return-really-stored-message-length.patch
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