ocfs2: validate inline xattr header before ibody lookups

Patch series "ocfs2: validate inline xattr header consumers".

Corrupt i_xattr_inline_size can move the computed inode-body xattr header
outside the dinode block. Several OCFS2 paths then trust xh_count or
xattr entry geometry from that unchecked header.

The reported KASAN splat hits the ibody lookup path:

  BUG: KASAN: use-after-free in ocfs2_xattr_find_entry+0x37b/0x3a0
  ocfs2_xattr_ibody_get()
  ocfs2_xattr_get_nolock()
  ocfs2_calc_xattr_init()

The same unchecked header derivation also exists in the outside-value
probe, ibody remove, inline refcount attach, and inline reflink paths.

This series factors the existing ibody list validation into a shared
helper and then converts the remaining inline-header consumers one at a
time.

Patch layout:

1. validate ibody get/find and reuse the helper in ibody list
2. validate the outside-value probe
3. validate ibody remove
4. validate inline refcount attach
5. validate inline reflink

This patch (of 5):

[BUG]
mknodat() can read past the end of a dinode block when ACL inheritance
walks a corrupted inode-body xattr header. Another report shows the same
unchecked lookup later faulting in the VFS open path after create
returns a garbage status.

KASAN: use-after-free in
ocfs2_xattr_find_entry+0x37b/0x3a0 fs/ocfs2/xattr.c:1078
Read of size 2 at addr ffff88801c520300 by task syz.0.10/360

Trace:
 ...
 ocfs2_xattr_find_entry+0x37b/0x3a0 fs/ocfs2/xattr.c:1078
 ocfs2_xattr_ibody_get fs/ocfs2/xattr.c:1178 [inline]
 ocfs2_xattr_get_nolock+0x2ee/0x1110 fs/ocfs2/xattr.c:1309
 ocfs2_calc_xattr_init+0x716/0xac0 fs/ocfs2/xattr.c:628
 ocfs2_mknod+0x935/0x2400 fs/ocfs2/namei.c:333
 ocfs2_create+0x158/0x390 fs/ocfs2/namei.c:676
 vfs_create fs/namei.c:3493 [inline]
 vfs_create+0x445/0x6f0 fs/namei.c:3477
 do_mknodat+0x2d8/0x5e0 fs/namei.c:4372
 __do_sys_mknodat fs/namei.c:4400 [inline]
 __se_sys_mknodat fs/namei.c:4397 [inline]
 __x64_sys_mknodat+0xb6/0xf0 fs/namei.c:4397
 ...

Another report:
 BUG: unable to handle page fault for address: fffffbfff3e40ec0
 RIP: 0010:__d_entry_type include/linux/dcache.h:414 [inline]
 RIP: 0010:d_can_lookup include/linux/dcache.h:429 [inline]
 RIP: 0010:d_is_dir include/linux/dcache.h:439 [inline]
 RIP: 0010:path_openat+0xe2f/0x2ce0 fs/namei.c:4134

Trace:
 ...
 do_filp_open+0x1f6/0x430 fs/namei.c:4161
 do_sys_openat2+0x117/0x1c0 fs/open.c:1437
 __x64_sys_openat+0x15b/0x220 fs/open.c:1463
 ...

[CAUSE]
ocfs2_xattr_ibody_list() already validates the inline xattr size and
entry count, but ocfs2_xattr_ibody_get() and ocfs2_xattr_ibody_find()
still derive the inline header directly from di->i_xattr_inline_size and
then trust xh_count. A corrupted inline size or entry count can therefore
move the computed header outside the dinode block before get/find start
walking it. That can either make ocfs2_xattr_find_entry() dereference
xs->header->xh_count outside the block or make ocfs2_xattr_get_nolock()
bubble a garbage status back through ocfs2_calc_xattr_init() into the
create/open path.

[FIX]
Factor the existing ibody header geometry checks into a shared helper.
Use it in ocfs2_xattr_ibody_get() and ocfs2_xattr_ibody_find(), and have
ocfs2_xattr_ibody_list() reuse the same helper instead of open-coding
the validation. Reject corrupt ibody metadata with -EFSCORRUPTED before
the lookup path can walk bogus xattr geometry or return a garbage status.

Link: https://lore.kernel.org/20260508085914.61647-1-gality369@gmail.com
Link: https://lore.kernel.org/20260508085914.61647-2-gality369@gmail.com
Signed-off-by: ZhengYuan Huang <gality369@gmail.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Jia-Ju Bai <baijiaju1990@gmail.com>
Cc: Zixuan Fu <r33s3n6@gmail.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 86cfd4c2adf923d1d8490814e2ac56ff69f5193f..3a5a17cdcf7eb93a39e808184f85ef1ba50f71ba 100644 (file)
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -950,6 +950,41 @@ static int ocfs2_xattr_list_entries(struct inode *inode,
        return result;
 }
 
+static int ocfs2_xattr_ibody_lookup_header(struct inode *inode,
+                                          struct ocfs2_dinode *di,
+                                          struct ocfs2_xattr_header **header)
+{
+       u16 xattr_count;
+       size_t max_entries;
+       u16 inline_size = le16_to_cpu(di->i_xattr_inline_size);
+
+       if (inline_size > inode->i_sb->s_blocksize ||
+           inline_size < sizeof(struct ocfs2_xattr_header)) {
+               ocfs2_error(inode->i_sb,
+                           "Invalid xattr inline size %u in inode %llu\n",
+                           inline_size,
+                           (unsigned long long)OCFS2_I(inode)->ip_blkno);
+               return -EFSCORRUPTED;
+       }
+
+       *header = (struct ocfs2_xattr_header *)
+               ((void *)di + inode->i_sb->s_blocksize - inline_size);
+
+       xattr_count = le16_to_cpu((*header)->xh_count);
+       max_entries = (inline_size - sizeof(struct ocfs2_xattr_header)) /
+                     sizeof(struct ocfs2_xattr_entry);
+
+       if (xattr_count > max_entries) {
+               ocfs2_error(inode->i_sb,
+                           "xattr entry count %u exceeds maximum %zu in inode %llu\n",
+                           xattr_count, max_entries,
+                           (unsigned long long)OCFS2_I(inode)->ip_blkno);
+               return -EFSCORRUPTED;
+       }
+
+       return 0;
+}
+
 int ocfs2_has_inline_xattr_value_outside(struct inode *inode,
                                         struct ocfs2_dinode *di)
 {
@@ -975,39 +1010,13 @@ static int ocfs2_xattr_ibody_list(struct inode *inode,
        struct ocfs2_xattr_header *header = NULL;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        int ret = 0;
-       u16 xattr_count;
-       size_t max_entries;
-       u16 inline_size;
 
        if (!(oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL))
                return ret;
 
-       inline_size = le16_to_cpu(di->i_xattr_inline_size);
-
-       /* Validate inline size is reasonable */
-       if (inline_size > inode->i_sb->s_blocksize ||
-           inline_size < sizeof(struct ocfs2_xattr_header)) {
-               ocfs2_error(inode->i_sb,
-                           "Invalid xattr inline size %u in inode %llu\n",
-                           inline_size,
-                           (unsigned long long)OCFS2_I(inode)->ip_blkno);
-               return -EFSCORRUPTED;
-       }
-
-       header = (struct ocfs2_xattr_header *)
-                ((void *)di + inode->i_sb->s_blocksize - inline_size);
-
-       xattr_count = le16_to_cpu(header->xh_count);
-       max_entries = (inline_size - sizeof(struct ocfs2_xattr_header)) /
-                      sizeof(struct ocfs2_xattr_entry);
-
-       if (xattr_count > max_entries) {
-               ocfs2_error(inode->i_sb,
-                           "xattr entry count %u exceeds maximum %zu in inode %llu\n",
-                           xattr_count, max_entries,
-                           (unsigned long long)OCFS2_I(inode)->ip_blkno);
-               return -EFSCORRUPTED;
-       }
+       ret = ocfs2_xattr_ibody_lookup_header(inode, di, &header);
+       if (ret)
+               return ret;
 
        ret = ocfs2_xattr_list_entries(inode, header, buffer, buffer_size);
 
@@ -1200,8 +1209,9 @@ static int ocfs2_xattr_ibody_get(struct inode *inode,
                return -ENODATA;
 
        xs->end = (void *)di + inode->i_sb->s_blocksize;
-       xs->header = (struct ocfs2_xattr_header *)
-                       (xs->end - le16_to_cpu(di->i_xattr_inline_size));
+       ret = ocfs2_xattr_ibody_lookup_header(inode, di, &xs->header);
+       if (ret)
+               return ret;
        xs->base = (void *)xs->header;
        xs->here = xs->header->xh_entries;
 
@@ -2726,12 +2736,14 @@ static int ocfs2_xattr_ibody_find(struct inode *inode,
 
        xs->xattr_bh = xs->inode_bh;
        xs->end = (void *)di + inode->i_sb->s_blocksize;
-       if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL)
-               xs->header = (struct ocfs2_xattr_header *)
-                       (xs->end - le16_to_cpu(di->i_xattr_inline_size));
-       else
+       if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL) {
+               ret = ocfs2_xattr_ibody_lookup_header(inode, di, &xs->header);
+               if (ret)
+                       return ret;
+       } else {
                xs->header = (struct ocfs2_xattr_header *)
                        (xs->end - OCFS2_SB(inode->i_sb)->s_xattr_inline_size);
+       }
        xs->base = (void *)xs->header;
        xs->here = xs->header->xh_entries;