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authorMaxim Levitsky <maximlevitsky@gmail.com>2007-09-27 20:34:09 -0300
committerMauro Carvalho Chehab <mchehab@infradead.org>2007-10-10 00:02:58 -0300
commit9900132f3437e9373aa030cdb5bd2d5db15566e3 (patch)
treeb4b450daf16d1f502869dd472ae2bad85892daca /drivers/media/video/videobuf-core.c
parent851c0c96b2212f48fe51afc1589541b5eae3a544 (diff)
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.c7
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(&current->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(&current->mm->mmap_sem);
+
return retval;
}