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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2016-09-23 22:57:13 -0400
committerSteven Rostedt <rostedt@goodmis.org>2016-09-25 10:27:08 -0400
commit1245800c0f96eb6ebb368593e251d66c01e61022 (patch)
treec945fb377258b480d806786d33fbd0f6ce118022 /kernel
parentc87edb36118664f1fa275107c1138b6f47793240 (diff)
downloadlinux-stericsson-1245800c0f96eb6ebb368593e251d66c01e61022.tar.gz
tracing: Move mutex to protect against resetting of seq data
The iter->seq can be reset outside the protection of the mutex. So can reading of user data. Move the mutex up to the beginning of the function. Fixes: d7350c3f45694 ("tracing/core: make the read callbacks reentrants") Cc: stable@vger.kernel.org # 2.6.30+ Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c15
1 files changed, 8 insertions, 7 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8a4bd6b68a0b..8fb4847b0450 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4890,19 +4890,20 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
struct trace_iterator *iter = filp->private_data;
ssize_t sret;
- /* return any leftover data */
- sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
- if (sret != -EBUSY)
- return sret;
-
- trace_seq_init(&iter->seq);
-
/*
* Avoid more than one consumer on a single file descriptor
* This is just a matter of traces coherency, the ring buffer itself
* is protected.
*/
mutex_lock(&iter->mutex);
+
+ /* return any leftover data */
+ sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
+ if (sret != -EBUSY)
+ goto out;
+
+ trace_seq_init(&iter->seq);
+
if (iter->trace->read) {
sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
if (sret)