On 2025/2/7 12:16, Darrick J. Wong wrote:
On Fri, Feb 07, 2025 at 11:27:43AM +0800, Ye Bin wrote:
From: Ye Bin <yebin10@xxxxxxxxxx>
There's issue as follows:
BUG: KASAN: use-after-free in ext4_xattr_inode_dec_ref_all+0x6ff/0x790
Read of size 4 at addr ffff88807b003000 by task syz-executor.0/15172
CPU: 3 PID: 15172 Comm: syz-executor.0
Call Trace:
__dump_stack lib/dump_stack.c:82 [inline]
dump_stack+0xbe/0xfd lib/dump_stack.c:123
print_address_description.constprop.0+0x1e/0x280 mm/kasan/report.c:400
__kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560
kasan_report+0x3a/0x50 mm/kasan/report.c:585
ext4_xattr_inode_dec_ref_all+0x6ff/0x790 fs/ext4/xattr.c:1137
ext4_xattr_delete_inode+0x4c7/0xda0 fs/ext4/xattr.c:2896
ext4_evict_inode+0xb3b/0x1670 fs/ext4/inode.c:323
evict+0x39f/0x880 fs/inode.c:622
iput_final fs/inode.c:1746 [inline]
iput fs/inode.c:1772 [inline]
iput+0x525/0x6c0 fs/inode.c:1758
ext4_orphan_cleanup fs/ext4/super.c:3298 [inline]
ext4_fill_super+0x8c57/0xba40 fs/ext4/super.c:5300
mount_bdev+0x355/0x410 fs/super.c:1446
legacy_get_tree+0xfe/0x220 fs/fs_context.c:611
vfs_get_tree+0x8d/0x2f0 fs/super.c:1576
do_new_mount fs/namespace.c:2983 [inline]
path_mount+0x119a/0x1ad0 fs/namespace.c:3316
do_mount+0xfc/0x110 fs/namespace.c:3329
__do_sys_mount fs/namespace.c:3540 [inline]
__se_sys_mount+0x219/0x2e0 fs/namespace.c:3514
do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x67/0xd1
Memory state around the buggy address:
ffff88807b002f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807b002f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807b003000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88807b003080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88807b003100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Above issue happens as ext4_xattr_delete_inode() isn't check xattr
is valid if xattr is in inode.
To solve above issue call xattr_check_inode() check if xattr if valid
in inode.
Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
fs/ext4/xattr.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 0e4494863d15..cb724477f8da 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2922,7 +2922,6 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
int extra_credits)
{
struct buffer_head *bh = NULL;
- struct ext4_xattr_ibody_header *header;
struct ext4_iloc iloc = { .bh = NULL };
struct ext4_xattr_entry *entry;
struct inode *ea_inode;
@@ -2937,6 +2936,9 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
if (ext4_has_feature_ea_inode(inode->i_sb) &&
ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
+ struct ext4_xattr_ibody_header *header;
+ struct ext4_inode *raw_inode;
+ void *end;
error = ext4_get_inode_loc(inode, &iloc);
if (error) {
@@ -2952,14 +2954,20 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
goto cleanup;
}
- header = IHDR(inode, ext4_raw_inode(&iloc));
- if (header->h_magic == cpu_to_le32(EXT4_XATTR_MAGIC))
+ raw_inode = ext4_raw_inode(&iloc);
+ header = IHDR(inode, raw_inode);
+ end = ITAIL(inode, raw_inode);
+ if (header->h_magic == cpu_to_le32(EXT4_XATTR_MAGIC)) {
This needs to make sure that header + sizeof(h_magic) >= end before
checking the magic number in header::h_magic, right?
--D
Thank you for your reply.
There ' s no need to check "header + sizeof(h_magic) >= end" because it
has been checked
when the EXT4_STATE_XATTR flag bit is set:
__ext4_iget
ret = ext4_iget_extra_inode(inode, raw_inode, ei);
if (EXT4_INODE_HAS_XATTR_SPACE(inode) && *magic ==
cpu_to_le32(EXT4_XATTR_MAGIC))
ext4_set_inode_state(inode, EXT4_STATE_XATTR);
It seems that the judgment of "header->h_magic ==
cpu_to_le32(EXT4_XATTR_MAGIC)"
should be redundant here.
+ error = xattr_check_inode(inode, header, end);
+ if (error)
+ goto cleanup;
ext4_xattr_inode_dec_ref_all(handle, inode, iloc.bh,
IFIRST(header),
false /* block_csum */,
ea_inode_array,
extra_credits,
false /* skip_quota */);
+ }
}
if (EXT4_I(inode)->i_file_acl) {
--
2.34.1
