This is a note to let you know that I've just added the patch titled fuse: do not use iocb after it may have been freed to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: fuse-do-not-use-iocb-after-it-may-have-been-freed.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7cabc61e01a0a8b663bd2b4c982aa53048218734 Mon Sep 17 00:00:00 2001 From: Robert Doebbelin <robert@xxxxxxxxxxx> Date: Mon, 7 Mar 2016 09:50:56 +0100 Subject: fuse: do not use iocb after it may have been freed From: Robert Doebbelin <robert@xxxxxxxxxxx> commit 7cabc61e01a0a8b663bd2b4c982aa53048218734 upstream. There's a race in fuse_direct_IO(), whereby is_sync_kiocb() is called on an iocb that could have been freed if async io has already completed. The fix in this case is simple and obvious: cache the result before starting io. It was discovered by KASan: kernel: ================================================================== kernel: BUG: KASan: use after free in fuse_direct_IO+0xb1a/0xcc0 at addr ffff88036c414390 Signed-off-by: Robert Doebbelin <robert@xxxxxxxxxxx> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> Fixes: bcba24ccdc82 ("fuse: enable asynchronous processing direct IO") Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/fuse/file.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2786,6 +2786,7 @@ fuse_direct_IO(struct kiocb *iocb, struc loff_t i_size; size_t count = iov_iter_count(iter); struct fuse_io_priv *io; + bool is_sync = is_sync_kiocb(iocb); pos = offset; inode = file->f_mapping->host; @@ -2825,11 +2826,11 @@ fuse_direct_IO(struct kiocb *iocb, struc * to wait on real async I/O requests, so we must submit this request * synchronously. */ - if (!is_sync_kiocb(iocb) && (offset + count > i_size) && + if (!is_sync && (offset + count > i_size) && iov_iter_rw(iter) == WRITE) io->async = false; - if (io->async && is_sync_kiocb(iocb)) + if (io->async && is_sync) io->done = &wait; if (iov_iter_rw(iter) == WRITE) { @@ -2843,7 +2844,7 @@ fuse_direct_IO(struct kiocb *iocb, struc fuse_aio_complete(io, ret < 0 ? ret : 0, -1); /* we have a non-extending, async request, so return */ - if (!is_sync_kiocb(iocb)) + if (!is_sync) return -EIOCBQUEUED; wait_for_completion(&wait); Patches currently in stable-queue which might be from robert@xxxxxxxxxxx are queue-4.4/fuse-do-not-use-iocb-after-it-may-have-been-freed.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html