CVE-2024-47701

In the Linux kernel, the following vulnerability has been resolved:

ext4: avoid OOB when system.data xattr changes underneath the filesystem

When looking up for an entry in an inlined directory, if e_value_offs is

changed underneath the filesystem by some change in the block device, it

will lead to an out-of-bounds access that KASAN detects as an UAF.

EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.

loop0: detected capacity change from 2048 to 2047

==================================================================

BUG: KASAN: use-after-free in ext4_search_dir+0xf2/0x1c0 fs/ext4/namei.c:1500

Read of size 1 at addr ffff88803e91130f by task syz-executor269/5103

CPU: 0 UID: 0 PID: 5103 Comm: syz-executor269 Not tainted 6.11.0-rc4-syzkaller #0

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014

Call Trace:

<TASK>

__dump_stack lib/dump_stack.c:93 [inline]

dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119

print_address_description mm/kasan/report.c:377 [inline]

print_report+0x169/0x550 mm/kasan/report.c:488

kasan_report+0x143/0x180 mm/kasan/report.c:601

ext4_search_dir+0xf2/0x1c0 fs/ext4/namei.c:1500

ext4_find_inline_entry+0x4be/0x5e0 fs/ext4/inline.c:1697

__ext4_find_entry+0x2b4/0x1b30 fs/ext4/namei.c:1573

ext4_lookup_entry fs/ext4/namei.c:1727 [inline]

ext4_lookup+0x15f/0x750 fs/ext4/namei.c:1795

lookup_one_qstr_excl+0x11f/0x260 fs/namei.c:1633

filename_create+0x297/0x540 fs/namei.c:3980

do_symlinkat+0xf9/0x3a0 fs/namei.c:4587

__do_sys_symlinkat fs/namei.c:4610 [inline]

__se_sys_symlinkat fs/namei.c:4607 [inline]

__x64_sys_symlinkat+0x95/0xb0 fs/namei.c:4607

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83

entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f3e73ced469

Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007fff4d40c258 EFLAGS: 00000246 ORIG_RAX: 000000000000010a

RAX: ffffffffffffffda RBX: 0032656c69662f2e RCX: 00007f3e73ced469

RDX: 0000000020000200 RSI: 00000000ffffff9c RDI: 00000000200001c0

RBP: 0000000000000000 R08: 00007fff4d40c290 R09: 00007fff4d40c290

R10: 0023706f6f6c2f76 R11: 0000000000000246 R12: 00007fff4d40c27c

R13: 0000000000000003 R14: 431bde82d7b634db R15: 00007fff4d40c2b0

</TASK>

Calling ext4_xattr_ibody_find right after reading the inode with

ext4_get_inode_loc will lead to a check of the validity of the xattrs,

avoiding this problem.