[lvc-project] [PATCH] fs: 9p: avoid warning during xattr allocation

[Fedor Pchelkin]

An invalid server may reply with an xattr size which still fits into
ssize_t but is large enough to cause splat during kzalloc().

Add __GFP_NOWARN flag for the allocation. It seems client side can't do
much more about sanity checking here so it's better to return ENOMEM
silently.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 85ff872d3f4a ("fs/9p: Implement POSIX ACL permission checking function")
Reported-by: syzbot+56fdf7f6291d819b9b19 at syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000789bcd05c9aa3d5d@google.com/
Reported-by: syzbot+a83dc51a78f0f4cf20da at syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/00000000000086a03405eec3a706@google.com/
Suggested-by: Pavel Skripkin <paskripkin at gmail.com>
Signed-off-by: Fedor Pchelkin <pchelkin at ispras.ru>
---
 fs/9p/acl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index eed551d8555f..e19a46192d2e 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -29,7 +29,7 @@ static struct posix_acl *v9fs_fid_get_acl(struct p9_fid *fid, const char *name)
 	if (size == 0)
 		return ERR_PTR(-ENODATA);
 
-	value = kzalloc(size, GFP_NOFS);
+	value = kzalloc(size, GFP_NOFS | __GFP_NOWARN);
 	if (!value)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.43.0