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ead6680f35
Once FD_ADD() returns, the fd is live in the file descriptor table and a thread sharing that table can close() it before DMA_BUF_TRACE() runs. The close drops the last reference, __fput() frees the dma_buf, and the tracepoint then dereferences dmabuf to take dmabuf->name_lock -- slab-use-after-free. Split FD_ADD() back into get_unused_fd_flags() + fd_install() and emit the tracepoint between them. While the fdtable slot is reserved with a NULL file pointer, a racing close() returns -EBADF without entering __fput(), so the dma_buf stays alive across the trace. Same approach as commit2d76319c4c("dma-buf: fix UAF in dma_buf_put() tracepoint"). This undoes the FD_ADD() conversion done in commit34dfce523c("dma: convert dma_buf_fd() to FD_ADD()"); FD_ADD() has no place to hook the tracepoint safely. Reported-by: syzbot+7f4987d0afb97dd090cb@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7f4987d0afb97dd090cb Fixes:281a226314("dma-buf: add some tracepoints to debug.") Cc: stable@vger.kernel.org # 7.0.x Signed-off-by: David Carlier <devnexen@gmail.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patch.msgid.link/20260523181446.69525-1-devnexen@gmail.com