linux-kernel - [RFC v2 2/4] xfs: add verifier check for symlink with append/immutable flags

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Date:   Thu, 10 May 2018 16:13:57 -0700
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     viro@...iv.linux.org.uk, darrick.wong@...cle.com, tytso@....edu,
        adilger.kernel@...ger.ca, clm@...com, jbacik@...com,
        dsterba@...e.com
Cc:     sandeen@...deen.net, dhowells@...hat.com, fliu@...e.com,
        jack@...e.cz, jeffm@...e.com, nborisov@...e.com,
        jake.norris@...e.com, mtk.manpages@...il.com,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [RFC v2 2/4] xfs: add verifier check for symlink with append/immutable flags

The Linux VFS does not allow a way to set append/immuttable attributes
to symlinks, this is just not possible. If this is detected we can
correct this with xfs_repair, so inform the user.

Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
 fs/xfs/libxfs/xfs_symlink_remote.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_symlink_remote.c b/fs/xfs/libxfs/xfs_symlink_remote.c
index 5ef5f354587e..42dd81ede3d6 100644
--- a/fs/xfs/libxfs/xfs_symlink_remote.c
+++ b/fs/xfs/libxfs/xfs_symlink_remote.c
@@ -242,5 +242,10 @@ xfs_symlink_shortform_verify(
 	/* We /did/ null-terminate the buffer, right? */
 	if (*endp != 0)
 		return __this_address;
+
+	/* Immutable and append flags are not allowed on symlinks */
+	if (ip->i_d.di_flags & (XFS_DIFLAG_APPEND | XFS_DIFLAG_IMMUTABLE))
+		return __this_address;
+
 	return NULL;
 }
-- 
2.17.0