[PATCH 6.6.y] xfs: fix buffer overruns in xfs_ioc_attr_list

[Sasha Levin <sashal@kernel.org>]

From: "Darrick J. Wong" <djwong@kernel.org>

[ Upstream commit 0b9081a774ee7b9dff1e9ac3765b73c1d6bba5b2 ]

When we converted the al_offset array in struct xfs_attrlist into a VLA,
the size of the object shrank by 4 bytes.  Unfortunately, the buffer
size validation in the attrlist ioctl wasn't updated to notice this, so
the al_offset[0] assignment blindly writes off the end of the buffer.
LOLLM noticed the omitted check and complained.

Cc: stable@vger.kernel.org # v6.5
Fixes: 371baf5c9750a2 ("xfs: convert flex-array declarations in struct xfs_attrlist*")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
[ sashal: Applied the unchanged fix at the existing xfs_ioc_attr_list() location because the upstream file split is absent. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/xfs/xfs_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 1d0c529255667..8f57f478a9b24 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -383,7 +383,7 @@ xfs_ioc_attr_list(
 	void				*buffer;
 	int				error;
 
-	if (bufsize < sizeof(struct xfs_attrlist) ||
+	if (bufsize < struct_size(alist, al_offset, 1) ||
 	    bufsize > XFS_XATTR_LIST_MAX)
 		return -EINVAL;
 
-- 
2.53.0