diff options
| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2016-09-23 22:57:13 -0400 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2016-11-20 01:01:42 +0000 |
| commit | e6711e36bb98f8538cadf8759a232cf49161fee6 (patch) | |
| tree | 38e0b18081e0b10235f14d08c43570bd6316aaa2 /kernel | |
| parent | 1f53d4c9835d7af7be92cdfc46b3062d051c1834 (diff) | |
tracing: Move mutex to protect against resetting of seq data
commit 1245800c0f96eb6ebb368593e251d66c01e61022 upstream.
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")
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f4b93a207026..ca7396e4aff4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3331,13 +3331,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, static struct tracer *old_tracer; 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); - /* copy the tracer to avoid using a global lock all around */ mutex_lock(&trace_types_lock); if (unlikely(old_tracer != current_trace && current_trace)) { @@ -3352,6 +3345,14 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, * 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) |