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Message-ID: <qqakibtcdtelsimkdghuoigdwtqhxwpii3ts5wohcw2qdt5rrz@vl2v72yxhk5n>
Date: Mon, 10 Feb 2025 17:47:44 +0100
From: Jan Kara <jack@...e.cz>
To: Ye Bin <yebin@...weicloud.com>
Cc: tytso@....edu, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
jack@...e.cz
Subject: Re: [PATCH v2 2/2] ext4: fix out-of-bound read in
ext4_xattr_inode_dec_ref_all()
On Sat 08-02-25 14:31:41, Ye Bin wrote:
> From: Ye Bin <yebin10@...wei.com>
>
> 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. In fact, we can directly verify in ext4_iget_extra_inode(),
> so that there is no divergent verification.
>
> Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
> Signed-off-by: Ye Bin <yebin10@...wei.com>
Nice! Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/ext4/inode.c | 5 +++++
> fs/ext4/xattr.c | 26 +-------------------------
> fs/ext4/xattr.h | 7 +++++++
> 3 files changed, 13 insertions(+), 25 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 7c54ae5fcbd4..af735386aa44 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4674,6 +4674,11 @@ static inline int ext4_iget_extra_inode(struct inode *inode,
> *magic == cpu_to_le32(EXT4_XATTR_MAGIC)) {
> int err;
>
> + err = xattr_check_inode(inode, IHDR(inode, raw_inode),
> + ITAIL(inode, raw_inode));
> + if (err)
> + return err;
> +
> ext4_set_inode_state(inode, EXT4_STATE_XATTR);
> err = ext4_find_inline_data_nolock(inode);
> if (!err && ext4_has_inline_data(inode))
> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index 0e4494863d15..a10fb8a9d02d 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c
> @@ -308,7 +308,7 @@ __ext4_xattr_check_block(struct inode *inode, struct buffer_head *bh,
> __ext4_xattr_check_block((inode), (bh), __func__, __LINE__)
>
>
> -static inline int
> +int
> __xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
> void *end, const char *function, unsigned int line)
> {
> @@ -316,9 +316,6 @@ __xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
> function, line);
> }
>
> -#define xattr_check_inode(inode, header, end) \
> - __xattr_check_inode((inode), (header), (end), __func__, __LINE__)
> -
> static int
> xattr_find_entry(struct inode *inode, struct ext4_xattr_entry **pentry,
> void *end, int name_index, const char *name, int sorted)
> @@ -650,9 +647,6 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
> raw_inode = ext4_raw_inode(&iloc);
> header = IHDR(inode, raw_inode);
> end = ITAIL(inode, raw_inode);
> - error = xattr_check_inode(inode, header, end);
> - if (error)
> - goto cleanup;
> entry = IFIRST(header);
> error = xattr_find_entry(inode, &entry, end, name_index, name, 0);
> if (error)
> @@ -783,7 +777,6 @@ ext4_xattr_ibody_list(struct dentry *dentry, char *buffer, size_t buffer_size)
> struct ext4_xattr_ibody_header *header;
> struct ext4_inode *raw_inode;
> struct ext4_iloc iloc;
> - void *end;
> int error;
>
> if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR))
> @@ -793,14 +786,9 @@ ext4_xattr_ibody_list(struct dentry *dentry, char *buffer, size_t buffer_size)
> return error;
> raw_inode = ext4_raw_inode(&iloc);
> header = IHDR(inode, raw_inode);
> - end = ITAIL(inode, raw_inode);
> - error = xattr_check_inode(inode, header, end);
> - if (error)
> - goto cleanup;
> error = ext4_xattr_list_entries(dentry, IFIRST(header),
> buffer, buffer_size);
>
> -cleanup:
> brelse(iloc.bh);
> return error;
> }
> @@ -868,7 +856,6 @@ int ext4_get_inode_usage(struct inode *inode, qsize_t *usage)
> struct ext4_xattr_ibody_header *header;
> struct ext4_xattr_entry *entry;
> qsize_t ea_inode_refs = 0;
> - void *end;
> int ret;
>
> lockdep_assert_held_read(&EXT4_I(inode)->xattr_sem);
> @@ -879,10 +866,6 @@ int ext4_get_inode_usage(struct inode *inode, qsize_t *usage)
> goto out;
> raw_inode = ext4_raw_inode(&iloc);
> header = IHDR(inode, raw_inode);
> - end = ITAIL(inode, raw_inode);
> - ret = xattr_check_inode(inode, header, end);
> - if (ret)
> - goto out;
>
> for (entry = IFIRST(header); !IS_LAST_ENTRY(entry);
> entry = EXT4_XATTR_NEXT(entry))
> @@ -2237,9 +2220,6 @@ int ext4_xattr_ibody_find(struct inode *inode, struct ext4_xattr_info *i,
> is->s.here = is->s.first;
> is->s.end = ITAIL(inode, raw_inode);
> if (ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
> - error = xattr_check_inode(inode, header, is->s.end);
> - if (error)
> - return error;
> /* Find the named attribute. */
> error = xattr_find_entry(inode, &is->s.here, is->s.end,
> i->name_index, i->name, 0);
> @@ -2790,10 +2770,6 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
> min_offs = end - base;
> total_ino = sizeof(struct ext4_xattr_ibody_header) + sizeof(u32);
>
> - error = xattr_check_inode(inode, header, end);
> - if (error)
> - goto cleanup;
> -
> ifree = ext4_xattr_free_space(base, &min_offs, base, &total_ino);
> if (ifree >= isize_diff)
> goto shift;
> diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
> index 5197f17ffd9a..1fedf44d4fb6 100644
> --- a/fs/ext4/xattr.h
> +++ b/fs/ext4/xattr.h
> @@ -209,6 +209,13 @@ extern int ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
> extern struct mb_cache *ext4_xattr_create_cache(void);
> extern void ext4_xattr_destroy_cache(struct mb_cache *);
>
> +extern int
> +__xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
> + void *end, const char *function, unsigned int line);
> +
> +#define xattr_check_inode(inode, header, end) \
> + __xattr_check_inode((inode), (header), (end), __func__, __LINE__)
> +
> #ifdef CONFIG_EXT4_FS_SECURITY
> extern int ext4_init_security(handle_t *handle, struct inode *inode,
> struct inode *dir, const struct qstr *qstr);
> --
> 2.34.1
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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