From: Jens Axboe <axboe@kernel.dk> mainline inclusion from mainline-v7.0-rc2 commit bfbc0b5b32a8f28ce284add619bf226716a59bc0 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13873 CVE: CVE-2026-23253 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- dvb_dvr_open() calls dvb_ringbuffer_init() when a new reader opens the DVR device. dvb_ringbuffer_init() calls init_waitqueue_head(), which reinitializes the waitqueue list head to empty. Since dmxdev->dvr_buffer.queue is a shared waitqueue (all opens of the same DVR device share it), this orphans any existing waitqueue entries from io_uring poll or epoll, leaving them with stale prev/next pointers while the list head is reset to {self, self}. The waitqueue and spinlock in dvr_buffer are already properly initialized once in dvb_dmxdev_init(). The open path only needs to reset the buffer data pointer, size, and read/write positions. Replace the dvb_ringbuffer_init() call in dvb_dvr_open() with direct assignment of data/size and a call to dvb_ringbuffer_reset(), which properly resets pread, pwrite, and error with correct memory ordering without touching the waitqueue or spinlock. Cc: stable@vger.kernel.org Fixes: 34731df288a5 ("V4L/DVB (3501): Dmxdev: use dvb_ringbuffer") Reported-by: syzbot+ab12f0c08dd7ab8d057c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ab12f0c08dd7ab8d057c Tested-by: syzbot+ab12f0c08dd7ab8d057c@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/698a26d3.050a0220.3b3015.007d.GAE@google.com/ Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Conflicts: drivers/media/dvb-core/dmxdev.c [context conflict] Signed-off-by: Chen Jinghuang <chenjinghuang2@huawei.com> --- drivers/media/dvb-core/dmxdev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c index 9ce5f010de3f..4ce3ae3954c5 100644 --- a/drivers/media/dvb-core/dmxdev.c +++ b/drivers/media/dvb-core/dmxdev.c @@ -168,7 +168,9 @@ static int dvb_dvr_open(struct inode *inode, struct file *file) mutex_unlock(&dmxdev->mutex); return -ENOMEM; } - dvb_ringbuffer_init(&dmxdev->dvr_buffer, mem, DVR_BUFFER_SIZE); + dmxdev->dvr_buffer.data = mem; + dmxdev->dvr_buffer.size = DVR_BUFFER_SIZE; + dvb_ringbuffer_reset(&dmxdev->dvr_buffer); if (dmxdev->may_do_mmap) dvb_vb2_init(&dmxdev->dvr_vb2_ctx, "dvr", file->f_flags & O_NONBLOCK); -- 2.34.1