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| author | Steven Rostedt <srostedt@redhat.com> | 2011-11-04 20:32:39 -0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2011-11-07 13:48:05 -0500 |
| commit | d4d34b981a5327eec956c6cb4cce397ce6f57279 (patch) | |
| tree | a5ee3ca4103b2a987f369a15cd9f28798d0d91cf | |
| parent | 49908a1b25d448d68fd26faca260e1850201575f (diff) | |
| download | lwn-d4d34b981a5327eec956c6cb4cce397ce6f57279.tar.gz lwn-d4d34b981a5327eec956c6cb4cce397ce6f57279.zip | |
ftrace: Fix hash record accounting bug
If the set_ftrace_filter is cleared by writing just whitespace to
it, then the filter hash refcounts will be decremented but not
updated. This causes two bugs:
1) No functions will be enabled for tracing when they all should be
2) If the users clears the set_ftrace_filter twice, it will crash ftrace:
------------[ cut here ]------------
WARNING: at /home/rostedt/work/git/linux-trace.git/kernel/trace/ftrace.c:1384 __ftrace_hash_rec_update.part.27+0x157/0x1a7()
Modules linked in:
Pid: 2330, comm: bash Not tainted 3.1.0-test+ #32
Call Trace:
[<ffffffff81051828>] warn_slowpath_common+0x83/0x9b
[<ffffffff8105185a>] warn_slowpath_null+0x1a/0x1c
[<ffffffff810ba362>] __ftrace_hash_rec_update.part.27+0x157/0x1a7
[<ffffffff810ba6e8>] ? ftrace_regex_release+0xa7/0x10f
[<ffffffff8111bdfe>] ? kfree+0xe5/0x115
[<ffffffff810ba51e>] ftrace_hash_move+0x2e/0x151
[<ffffffff810ba6fb>] ftrace_regex_release+0xba/0x10f
[<ffffffff8112e49a>] fput+0xfd/0x1c2
[<ffffffff8112b54c>] filp_close+0x6d/0x78
[<ffffffff8113a92d>] sys_dup3+0x197/0x1c1
[<ffffffff8113a9a6>] sys_dup2+0x4f/0x54
[<ffffffff8150cac2>] system_call_fastpath+0x16/0x1b
---[ end trace 77a3a7ee73794a02 ]---
Link: http://lkml.kernel.org/r/20111101141420.GA4918@debian
Reported-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/ftrace.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 0fcc6caead1c..7caa4505508d 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1210,7 +1210,9 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable, if (!src->count) { free_ftrace_hash_rcu(*dst); rcu_assign_pointer(*dst, EMPTY_HASH); - return 0; + /* still need to update the function records */ + ret = 0; + goto out; } /* |