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authorJesper Juhl <jesper.juhl@gmail.com>2006-06-23 12:27:36 -0400
committerMauro Carvalho Chehab <mchehab@infradead.org>2006-06-25 01:05:14 -0400
commitbafefc0cf8e4b34fbb159ea2e2aef2358ebff935 (patch)
treeb4099efa66238c30f0bd94a2a4c7c86c30c5fe59 /drivers/media/video/cpia2
parent7597e8e71f897449a26d5a32eedc09f8e76ae52a (diff)
V4L/DVB (4154): Fix use-after-free bug in cpia2 driver
The coverity checker detected a use-after-free error in drivers/media/video/cpia2/cpia2_v4l.c::cpia2_close() (coverity error #1281). What happens is that we lock cam->busy_lock, then proceed to free resources, and in the case of (--cam->open_count == 0) we finish off by doing a kfree(cam) and then at the end of the function we do a mutex_unlock(&cam->busy_lock) which will explode since it'll dereference the free'd `cam' : ... mutex_lock(&cam->busy_lock); ... if (--cam->open_count == 0) { ... if (!cam->present) { video_unregister_device(dev); kfree(cam); } } mutex_unlock(&cam->busy_lock); <--- PROBLEM, cam no longer around. ... Since this only happens in the case of open_count going down to zero I don't see a problem with just releasing the mutex after unregistering the device and just before the kfree(). In this case there is nothing around that we can race against; we are in the release method, open_count is zero, (!cam->present) and the device has just been unregistered, so letting go of the mutex at this point looks safe to me. Patch below to implement that solution. Acked-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'drivers/media/video/cpia2')
-rw-r--r--drivers/media/video/cpia2/cpia2_v4l.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/media/video/cpia2/cpia2_v4l.c b/drivers/media/video/cpia2/cpia2_v4l.c
index 28d93c595df0..d129db57fcd4 100644
--- a/drivers/media/video/cpia2/cpia2_v4l.c
+++ b/drivers/media/video/cpia2/cpia2_v4l.c
@@ -343,7 +343,9 @@ static int cpia2_close(struct inode *inode, struct file *file)
343 cpia2_free_buffers(cam); 343 cpia2_free_buffers(cam);
344 if (!cam->present) { 344 if (!cam->present) {
345 video_unregister_device(dev); 345 video_unregister_device(dev);
346 mutex_unlock(&cam->busy_lock);
346 kfree(cam); 347 kfree(cam);
348 return 0;
347 } 349 }
348 } 350 }
349 351