[PATCH v3 1/4] ext4: fix WARNING in ext4_expand_extra_isize_ea

[Ye Bin]

From: Ye Bin <yebin10@xxxxxxxxxx>

Syzbot found the following issue:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 3631 at mm/page_alloc.c:5534 __alloc_pages+0x30a/0x560 mm/page_alloc.c:5534
Modules linked in:
CPU: 1 PID: 3631 Comm: syz-executor261 Not tainted 6.1.0-rc6-syzkaller-00308-g644e9524388a #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:__alloc_pages+0x30a/0x560 mm/page_alloc.c:5534
RSP: 0018:ffffc90003ccf080 EFLAGS: 00010246
RAX: ffffc90003ccf0e0 RBX: 000000000000000c RCX: 0000000000000000
RDX: 0000000000000028 RSI: 0000000000000000 RDI: ffffc90003ccf108
RBP: ffffc90003ccf198 R08: dffffc0000000000 R09: ffffc90003ccf0e0
R10: fffff52000799e21 R11: 1ffff92000799e1c R12: 0000000000040c40
R13: 1ffff92000799e18 R14: dffffc0000000000 R15: 1ffff92000799e14
FS:  0000555555c10300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc36f70000 CR3: 00000000744ad000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __alloc_pages_node include/linux/gfp.h:223 [inline]
 alloc_pages_node include/linux/gfp.h:246 [inline]
 __kmalloc_large_node+0x8a/0x1a0 mm/slab_common.c:1096
 __do_kmalloc_node mm/slab_common.c:943 [inline]
 __kmalloc+0xfe/0x1a0 mm/slab_common.c:968
 kmalloc include/linux/slab.h:558 [inline]
 ext4_xattr_move_to_block fs/ext4/xattr.c:2558 [inline]
 ext4_xattr_make_inode_space fs/ext4/xattr.c:2673 [inline]
 ext4_expand_extra_isize_ea+0xe3f/0x1cd0 fs/ext4/xattr.c:2765
 __ext4_expand_extra_isize+0x2b8/0x3f0 fs/ext4/inode.c:5857
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5900 [inline]
 __ext4_mark_inode_dirty+0x51a/0x670 fs/ext4/inode.c:5978
 ext4_inline_data_truncate+0x548/0xd00 fs/ext4/inline.c:2021
 ext4_truncate+0x341/0xeb0 fs/ext4/inode.c:4221
 ext4_process_orphan+0x1aa/0x2d0 fs/ext4/orphan.c:339
 ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474
 __ext4_fill_super fs/ext4/super.c:5515 [inline]
 ext4_fill_super+0x80ed/0x8610 fs/ext4/super.c:5643
 get_tree_bdev+0x400/0x620 fs/super.c:1324
 vfs_get_tree+0x88/0x270 fs/super.c:1531
 do_new_mount+0x289/0xad0 fs/namespace.c:3040
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
 </TASK>

Reason is allocate 16M memory by kmalloc, but MAX_ORDER is 11, kmalloc
can allocate maximum size memory is 4M.
XATTR_SIZE_MAX is currently 64K, but EXT4_XATTR_SIZE_MAX is 16M, so
'ext4_xattr_check_entries()' regards this length as legal. Then trigger
warning in 'ext4_xattr_move_to_block()'.
To solve above issue, change EXT4_XATTR_SIZE_MAX from 16M to 64K.
As VFS limit extended attribute maximum size to 64K. So we can assume
that there will be no extended attribute with a length greater than 64K.

Reported-by: syzbot+4d99a966fd74bdeeec36@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 54dd0e0a1b25 ("ext4: add extra checks to ext4_xattr_block_get()")
Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
 fs/ext4/xattr.h | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
index 824faf0b15a8..c71e582b1007 100644
--- a/fs/ext4/xattr.h
+++ b/fs/ext4/xattr.h
@@ -71,15 +71,10 @@ struct ext4_xattr_entry {
 #define IFIRST(hdr) ((struct ext4_xattr_entry *)((hdr)+1))
 
 /*
- * XATTR_SIZE_MAX is currently 64k, but for the purposes of checking
- * for file system consistency errors, we use a somewhat bigger value.
- * This allows XATTR_SIZE_MAX to grow in the future, but by using this
- * instead of INT_MAX for certain consistency checks, we don't need to
- * worry about arithmetic overflows.  (Actually XATTR_SIZE_MAX is
- * defined in include/uapi/linux/limits.h, so changing it is going
- * not going to be trivial....)
+ * Use XATTR_SIZE_MAX to checking for file system consistency errors. Extended
+ * attribute length exceed XATTR_SIZE_MAX is illegal.
  */
-#define EXT4_XATTR_SIZE_MAX (1 << 24)
+#define EXT4_XATTR_SIZE_MAX XATTR_SIZE_MAX
 
 /*
  * The minimum size of EA value when you start storing it in an external inode
-- 
2.31.1