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Message-Id: <20240821152324.3621860-5-cascardo@igalia.com>
Date: Wed, 21 Aug 2024 12:23:24 -0300
From: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
To: linux-ext4@...r.kernel.org
Cc: Theodore Ts'o <tytso@....edu>,
linux-kernel@...r.kernel.org,
Tao Ma <boyu.mt@...bao.com>,
Andreas Dilger <adilger.kernel@...ger.ca>,
kernel-dev@...lia.com,
Thadeu Lima de Souza Cascardo <cascardo@...lia.com>,
syzbot+0c2508114d912a54ee79@...kaller.appspotmail.com
Subject: [PATCH 4/4] 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.
Reported-by: syzbot+0c2508114d912a54ee79@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0c2508114d912a54ee79
Fixes: e8e948e7802a ("ext4: let ext4_find_entry handle inline data")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
---
fs/ext4/inline.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 7b98b1bf1dc9..44a5f6df59ec 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -1664,25 +1664,36 @@ struct buffer_head *ext4_find_inline_entry(struct inode *dir,
struct ext4_dir_entry_2 **res_dir,
int *has_inline_data)
{
+ struct ext4_xattr_ibody_find is = {
+ .s = { .not_found = -ENODATA, },
+ };
+ struct ext4_xattr_info i = {
+ .name_index = EXT4_XATTR_INDEX_SYSTEM,
+ .name = EXT4_XATTR_SYSTEM_DATA,
+ };
int ret;
- struct ext4_iloc iloc;
void *inline_start;
int inline_size;
- ret = ext4_get_inode_loc(dir, &iloc);
+ ret = ext4_get_inode_loc(dir, &is.iloc);
if (ret)
return ERR_PTR(ret);
down_read(&EXT4_I(dir)->xattr_sem);
+
+ ret = ext4_xattr_ibody_find(dir, &i, &is);
+ if (ret)
+ goto out;
+
if (!ext4_has_inline_data(dir)) {
*has_inline_data = 0;
goto out;
}
- inline_start = (void *)ext4_raw_inode(&iloc)->i_block +
+ inline_start = (void *)ext4_raw_inode(&is.iloc)->i_block +
EXT4_INLINE_DOTDOT_SIZE;
inline_size = EXT4_MIN_INLINE_DATA_SIZE - EXT4_INLINE_DOTDOT_SIZE;
- ret = ext4_search_dir(iloc.bh, inline_start, inline_size,
+ ret = ext4_search_dir(is.iloc.bh, inline_start, inline_size,
dir, fname, 0, res_dir);
if (ret == 1)
goto out_find;
@@ -1692,23 +1703,23 @@ struct buffer_head *ext4_find_inline_entry(struct inode *dir,
if (ext4_get_inline_size(dir) == EXT4_MIN_INLINE_DATA_SIZE)
goto out;
- inline_start = ext4_get_inline_xattr_pos(dir, &iloc);
+ inline_start = ext4_get_inline_xattr_pos(dir, &is.iloc);
inline_size = ext4_get_inline_size(dir) - EXT4_MIN_INLINE_DATA_SIZE;
- ret = ext4_search_dir(iloc.bh, inline_start, inline_size,
+ ret = ext4_search_dir(is.iloc.bh, inline_start, inline_size,
dir, fname, 0, res_dir);
if (ret == 1)
goto out_find;
out:
- brelse(iloc.bh);
+ brelse(is.iloc.bh);
if (ret < 0)
- iloc.bh = ERR_PTR(ret);
+ is.iloc.bh = ERR_PTR(ret);
else
- iloc.bh = NULL;
+ is.iloc.bh = NULL;
out_find:
up_read(&EXT4_I(dir)->xattr_sem);
- return iloc.bh;
+ return is.iloc.bh;
}
int ext4_delete_inline_entry(handle_t *handle,
--
2.34.1
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