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| author |   Maxim Levitsky <maximlevitsky@gmail.com> | 2007-09-27 20:34:09 -0300 |
|---|---|---|
| committer |   Mauro Carvalho Chehab <mchehab@infradead.org> | 2007-10-10 00:02:58 -0300 |
| commit | 9900132f3437e9373aa030cdb5bd2d5db15566e3 (patch) | |
| tree | b4b450daf16d1f502869dd472ae2bad85892daca /drivers/media/video/videobuf-core.c | |
| parent | V4L/DVB (6266): videobuf cleanup: mmap check is common to all videobuf. Make it at core (diff) | |
| download | linux-dev-9900132f3437e9373aa030cdb5bd2d5db15566e3.tar.xz linux-dev-9900132f3437e9373aa030cdb5bd2d5db15566e3.zip | |
V4L/DVB (6268): V4L: Fix a lock inversion in generic videobuf code
videobuf_qbuf takes q->lock, and then calls
q->ops->buf_prepare which by design in all drivers calls
videobuf_iolock which calls videobuf_dma_init_user and this
takes current->mm->mmap_sem
on the other hand if user calls mumap from other thread, sys_munmap
takes current->mm->mmap_sem and videobuf_vm_close takes q->lock
Since this can occur only for V4L2_MEMORY_MMAP buffers, take
current->mm->mmap_sem in qbuf, before q->lock, and don't take
current->mm->mmap_sem videobuf_dma_init_user for those buffers
Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
http://thread.gmane.org/gmane.comp.video.video4linux/34978/focus=34981
Reviewed-by: Ricardo Cerqueira <v4l@cerqueira.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'drivers/media/video/videobuf-core.c')
| -rw-r--r-- | drivers/media/video/videobuf-core.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/media/video/videobuf-core.c b/drivers/media/video/videobuf-core.c index 3bd06bb633a7..a27e114cacef 100644 --- a/drivers/media/video/videobuf-core.c +++ b/drivers/media/video/videobuf-core.c @@ -349,6 +349,9 @@ int videobuf_qbuf(struct videobuf_queue *q, MAGIC_CHECK(q->int_ops->magic,MAGIC_QTYPE_OPS); + if (b->memory == V4L2_MEMORY_MMAP) + down_read(¤t->mm->mmap_sem); + mutex_lock(&q->lock); retval = -EBUSY; if (q->reading) { @@ -434,6 +437,10 @@ int videobuf_qbuf(struct videobuf_queue *q, done: mutex_unlock(&q->lock); + + if (b->memory == V4L2_MEMORY_MMAP) + up_read(¤t->mm->mmap_sem); + return retval; } |