The patch titled
Subject: ocfs2: remove entry once instead of null-ptr-dereference in ocfs2_xa_remove()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
ocfs2-remove-entry-once-instead-of-null-ptr-dereference-in-ocfs2_xa_remove.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-remove-entry-once-instead-of-null-ptr-dereference-in-ocfs2_xa_remove.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Andrew Kanner <andrew.kanner@xxxxxxxxx>
Subject: ocfs2: remove entry once instead of null-ptr-dereference in ocfs2_xa_remove()
Date: Sun, 3 Nov 2024 20:38:45 +0100
Syzkaller is able to provoke null-ptr-dereference in ocfs2_xa_remove():
[ 57.319872] (a.out,1161,7):ocfs2_xa_remove:2028 ERROR: status = -12
[ 57.320420] (a.out,1161,7):ocfs2_xa_cleanup_value_truncate:1999 ERROR: Partial truncate while removing xattr overlay.upper. Leaking 1 clusters and removing the entry
[ 57.321727] BUG: kernel NULL pointer dereference, address: 0000000000000004
[...]
[ 57.325727] RIP: 0010:ocfs2_xa_block_wipe_namevalue+0x2a/0xc0
[...]
[ 57.331328] Call Trace:
[ 57.331477] <TASK>
[...]
[ 57.333511] ? do_user_addr_fault+0x3e5/0x740
[ 57.333778] ? exc_page_fault+0x70/0x170
[ 57.334016] ? asm_exc_page_fault+0x2b/0x30
[ 57.334263] ? __pfx_ocfs2_xa_block_wipe_namevalue+0x10/0x10
[ 57.334596] ? ocfs2_xa_block_wipe_namevalue+0x2a/0xc0
[ 57.334913] ocfs2_xa_remove_entry+0x23/0xc0
[ 57.335164] ocfs2_xa_set+0x704/0xcf0
[ 57.335381] ? _raw_spin_unlock+0x1a/0x40
[ 57.335620] ? ocfs2_inode_cache_unlock+0x16/0x20
[ 57.335915] ? trace_preempt_on+0x1e/0x70
[ 57.336153] ? start_this_handle+0x16c/0x500
[ 57.336410] ? preempt_count_sub+0x50/0x80
[ 57.336656] ? _raw_read_unlock+0x20/0x40
[ 57.336906] ? start_this_handle+0x16c/0x500
[ 57.337162] ocfs2_xattr_block_set+0xa6/0x1e0
[ 57.337424] __ocfs2_xattr_set_handle+0x1fd/0x5d0
[ 57.337706] ? ocfs2_start_trans+0x13d/0x290
[ 57.337971] ocfs2_xattr_set+0xb13/0xfb0
[ 57.338207] ? dput+0x46/0x1c0
[ 57.338393] ocfs2_xattr_trusted_set+0x28/0x30
[ 57.338665] ? ocfs2_xattr_trusted_set+0x28/0x30
[ 57.338948] __vfs_removexattr+0x92/0xc0
[ 57.339182] __vfs_removexattr_locked+0xd5/0x190
[ 57.339456] ? preempt_count_sub+0x50/0x80
[ 57.339705] vfs_removexattr+0x5f/0x100
[...]
Reproducer uses faultinject facility to fail ocfs2_xa_remove() ->
ocfs2_xa_value_truncate() with -ENOMEM.
In this case the comment mentions that we can return 0 if
ocfs2_xa_cleanup_value_truncate() is going to wipe the entry
anyway. But the following 'rc' check is wrong and execution flow do
'ocfs2_xa_remove_entry(loc);' twice:
* 1st: in ocfs2_xa_cleanup_value_truncate();
* 2nd: returning back to ocfs2_xa_remove() instead of going to 'out'.
Fix this by skipping the 2nd removal of the same entry and making
syzkaller repro happy.
Link: https://lkml.kernel.org/r/20241103193845.2940988-1-andrew.kanner@xxxxxxxxx
Fixes: 399ff3a748cf ("ocfs2: Handle errors while setting external xattr values.")
Signed-off-by: Andrew Kanner <andrew.kanner@xxxxxxxxx>
Reported-by: syzbot+386ce9e60fa1b18aac5b@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/671e13ab.050a0220.2b8c0f.01d0.GAE@xxxxxxxxxx/T/
Tested-by: syzbot+386ce9e60fa1b18aac5b@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Mark Fasheh <mark@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Changwei Ge <gechangwei@xxxxxxx>
Cc: Gang He <ghe@xxxxxxxx>
Cc: Jun Piao <piaojun@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/xattr.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/fs/ocfs2/xattr.c~ocfs2-remove-entry-once-instead-of-null-ptr-dereference-in-ocfs2_xa_remove
+++ a/fs/ocfs2/xattr.c
@@ -2036,8 +2036,7 @@ static int ocfs2_xa_remove(struct ocfs2_
rc = 0;
ocfs2_xa_cleanup_value_truncate(loc, "removing",
orig_clusters);
- if (rc)
- goto out;
+ goto out;
}
}
_
Patches currently in -mm which might be from andrew.kanner@xxxxxxxxx are
ocfs2-remove-entry-once-instead-of-null-ptr-dereference-in-ocfs2_xa_remove.patch
