| From | Jiri Slaby <> | Subject | [PATCH 3.12 229/235] fuse: do not use iocb after it may have been freed | Date | Fri, 27 Jan 2017 11:56:02 +0100 |
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From: Robert Doebbelin <robert@quobyte.com>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
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@quobyte.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Fixes: bcba24ccdc82 ("fuse: enable asynchronous processing direct IO") Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- fs/fuse/file.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 8ef52e12cd57..f6314cd3e3b0 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2393,6 +2393,7 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t i_size; size_t count = iov_length(iov, nr_segs); struct fuse_io_priv *io; + bool is_sync = is_sync_kiocb(iocb); pos = offset; inode = file->f_mapping->host; @@ -2428,7 +2429,7 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, * to wait on real async I/O requests, so we must submit this request * synchronously. */ - if (!is_sync_kiocb(iocb) && (offset + count > i_size) && rw == WRITE) + if (!is_sync && (offset + count > i_size) && rw == WRITE) io->async = false; if (rw == WRITE) @@ -2440,7 +2441,7 @@ fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, 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; ret = wait_on_sync_kiocb(iocb); -- 2.11.0
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