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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2013-07-01 22:50:29 -0400
committerSteven Rostedt <rostedt@goodmis.org>2013-07-02 09:58:11 -0400
commitff451961a8b2a17667a7bfa39c86fb9b351445db (patch)
tree03f82366f860605664b4a7fe11a97f57fc0632a8 /kernel/kmod.c
parenta82274151af2b075163e3c42c828529dee311487 (diff)
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tracing: Add trace_array_get/put() to handle instance refs better
Commit a695cb58162 "tracing: Prevent deleting instances when they are being read" tried to fix a race between deleting a trace instance and reading contents of a trace file. But it wasn't good enough. The following could crash the kernel: # cd /sys/kernel/debug/tracing/instances # ( while :; do mkdir foo; rmdir foo; done ) & # ( while :; do cat foo/trace &> /dev/null; done ) & Luckily this can only be done by root user, but it should be fixed regardless. The problem is that a delete of the file can happen after the reader starts to open the file but before it grabs the trace_types_mutex. The solution is to validate the trace array before using it. If the trace array does not exist in the list of trace arrays, then it returns -ENODEV. There's a possibility that a trace_array could be deleted and a new one created and the open would open its file instead. But that is very minor as it will just return the data of the new trace array, it may confuse the user but it will not crash the system. As this can only be done by root anyway, the race will only occur if root is deleting what its trying to read at the same time. Cc: stable@vger.kernel.org # 3.10 Reported-by: Alexander Lam <azl@google.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/kmod.c')
0 files changed, 0 insertions, 0 deletions
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