From: Robert Doebbelin Date: Mon, 7 Mar 2016 08:50:56 +0000 (+0100) Subject: fuse: do not use iocb after it may have been freed X-Git-Tag: v4.1.12-92~150^2~48 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=88bdf1a2c491297a5960ea1b2dc6cdf4e04afe74;p=users%2Fjedix%2Flinux-maple.git fuse: do not use iocb after it may have been freed Orabug: 23331110 [ Upstream commit 7cabc61e01a0a8b663bd2b4c982aa53048218734 ] 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 Signed-off-by: Miklos Szeredi Fixes: bcba24ccdc82 ("fuse: enable asynchronous processing direct IO") Cc: # 3.10+ Signed-off-by: Sasha Levin (cherry picked from commit 19167d65fabb60ff11fc5f9c4a5248c17a12f615) Signed-off-by: Dan Duval --- diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 5ef05b5c4cff8..e30b4c4fd81a4 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2786,6 +2786,7 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset) 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, struct iov_iter *iter, loff_t offset) * 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, struct iov_iter *iter, loff_t offset) 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);