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fuse: handle zero sized retrieve correctly

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commit 97e1532ef8 upstream.

Dereferencing req->page_descs[0] will Oops if req->max_pages is zero.

Reported-by: syzbot+c1e36d30ee3416289cc0@syzkaller.appspotmail.com
Tested-by: syzbot+c1e36d30ee3416289cc0@syzkaller.appspotmail.com
Fixes: b2430d7567 ("fuse: add per-page descriptor <offset, length> to fuse_req")
Cc: <stable@vger.kernel.org> # v3.9
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Miklos Szeredi
2019-01-16 10:27:59 +01:00
committed by Greg Kroah-Hartman
parent bade8e5f26
commit c5cf17c81d
1 changed files with 1 additions and 1 deletions
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2
fs/fuse/dev.c
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@@ -1741,7 +1741,6 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
req->in.h.nodeid = outarg->nodeid;
req->in.numargs = 2;
req->in.argpages = 1;
req->page_descs[0].offset = offset;
req->end = fuse_retrieve_end;
index = outarg->offset >> PAGE_CACHE_SHIFT;
@@ -1756,6 +1755,7 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
req->pages[req->num_pages] = page;
req->page_descs[req->num_pages].offset = offset;
req->page_descs[req->num_pages].length = this_num;
req->num_pages++;