| From | Ben Hutchings <> | Date | Wed, 27 Apr 2016 01:02:21 +0200 | Subject | [PATCH 3.16 097/217] fuse: do not use iocb after it may have been freed |
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3.16.35-rc1 review patch. If anyone has any objections, please let me know.
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From: Robert Doebbelin <robert@quobyte.com>
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") [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- fs/fuse/file.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2876,6 +2876,7 @@ fuse_direct_IO(int rw, struct kiocb *ioc 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; @@ -2915,7 +2916,7 @@ fuse_direct_IO(int rw, struct kiocb *ioc * 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) @@ -2927,7 +2928,7 @@ fuse_direct_IO(int rw, struct kiocb *ioc 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);
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