From: Ahmet Eray Karadag <eraykrdg1@gmail.com> stable inclusion from stable-v5.10.246 commit 1cfb3e4ddbdc8e02e637b8852540bd4718bf4814 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICXMCD CVE: CVE-2025-40190 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 57295e835408d8d425bef58da5253465db3d6888 upstream. syzkaller found a path where ext4_xattr_inode_update_ref() reads an EA inode refcount that is already <= 0 and then applies ref_change (often -1). That lets the refcount underflow and we proceed with a bogus value, triggering errors like: EXT4-fs error: EA inode <n> ref underflow: ref_count=-1 ref_change=-1 EXT4-fs warning: ea_inode dec ref err=-117 Make the invariant explicit: if the current refcount is non-positive, treat this as on-disk corruption, emit ext4_error_inode(), and fail the operation with -EFSCORRUPTED instead of updating the refcount. Delete the WARN_ONCE() as negative refcounts are now impossible; keep error reporting in ext4_error_inode(). This prevents the underflow and the follow-on orphan/cleanup churn. Reported-by: syzbot+0be4f339a8218d2a5bb1@syzkaller.appspotmail.com Fixes: https://syzbot.org/bug?extid=0be4f339a8218d2a5bb1 Cc: stable@kernel.org Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com> Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com> Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com> Message-ID: <20250920021342.45575-1-eraykrdg1@gmail.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Liu Mingrui <liumingrui@huawei.com> Signed-off-by: Zizhi Wo <wozizhi@huawei.com> --- fs/ext4/xattr.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index bacd36b78134..4e25463db664 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -983,7 +983,7 @@ static int ext4_xattr_inode_update_ref(handle_t *handle, struct inode *ea_inode, int ref_change) { struct ext4_iloc iloc; - s64 ref_count; + u64 ref_count; int ret; inode_lock_nested(ea_inode, I_MUTEX_XATTR); @@ -993,13 +993,17 @@ static int ext4_xattr_inode_update_ref(handle_t *handle, struct inode *ea_inode, goto out; ref_count = ext4_xattr_inode_get_ref(ea_inode); + if ((ref_count == 0 && ref_change < 0) || (ref_count == U64_MAX && ref_change > 0)) { + ext4_error_inode(ea_inode, __func__, __LINE__, 0, + "EA inode %lu ref wraparound: ref_count=%lld ref_change=%d", + ea_inode->i_ino, ref_count, ref_change); + ret = -EFSCORRUPTED; + goto out; + } ref_count += ref_change; ext4_xattr_inode_set_ref(ea_inode, ref_count); if (ref_change > 0) { - WARN_ONCE(ref_count <= 0, "EA inode %lu ref_count=%lld", - ea_inode->i_ino, ref_count); - if (ref_count == 1) { WARN_ONCE(ea_inode->i_nlink, "EA inode %lu i_nlink=%u", ea_inode->i_ino, ea_inode->i_nlink); @@ -1008,9 +1012,6 @@ static int ext4_xattr_inode_update_ref(handle_t *handle, struct inode *ea_inode, ext4_orphan_del(handle, ea_inode); } } else { - WARN_ONCE(ref_count < 0, "EA inode %lu ref_count=%lld", - ea_inode->i_ino, ref_count); - if (ref_count == 0) { WARN_ONCE(ea_inode->i_nlink != 1, "EA inode %lu i_nlink=%u", -- 2.39.2