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
> + 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
>
>
