diff options
| author | Deepanshu Kartikey <kartikey406@gmail.com> | 2025-10-20 11:39:36 +0530 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2025-11-13 08:25:04 -0500 |
| commit | 892e1cf17555735e9d021ab036c36bc7b58b0e3b (patch) | |
| tree | d76d898defe5f455a08fa33930b7bfd2763ad509 /fs/ext4/inline.c | |
| parent | 9dbf945320b11c5865d2f550f8e972566d04d181 (diff) | |
ext4: refresh inline data size before write operations
The cached ei->i_inline_size can become stale between the initial size
check and when ext4_update_inline_data()/ext4_create_inline_data() use
it. Although ext4_get_max_inline_size() reads the correct value at the
time of the check, concurrent xattr operations can modify i_inline_size
before ext4_write_lock_xattr() is acquired.
This causes ext4_update_inline_data() and ext4_create_inline_data() to
work with stale capacity values, leading to a BUG_ON() crash in
ext4_write_inline_data():
kernel BUG at fs/ext4/inline.c:1331!
BUG_ON(pos + len > EXT4_I(inode)->i_inline_size);
The race window:
1. ext4_get_max_inline_size() reads i_inline_size = 60 (correct)
2. Size check passes for 50-byte write
3. [Another thread adds xattr, i_inline_size changes to 40]
4. ext4_write_lock_xattr() acquires lock
5. ext4_update_inline_data() uses stale i_inline_size = 60
6. Attempts to write 50 bytes but only 40 bytes actually available
7. BUG_ON() triggers
Fix this by recalculating i_inline_size via ext4_find_inline_data_nolock()
immediately after acquiring xattr_sem. This ensures ext4_update_inline_data()
and ext4_create_inline_data() work with current values that are protected
from concurrent modifications.
This is similar to commit a54c4613dac1 ("ext4: fix race writing to an
inline_data file while its xattrs are changing") which fixed i_inline_off
staleness. This patch addresses the related i_inline_size staleness issue.
Reported-by: syzbot+f3185be57d7e8dda32b8@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=f3185be57d7e8dda32b8
Cc: stable@kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Message-ID: <20251020060936.474314-1-kartikey406@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/inline.c')
| -rw-r--r-- | fs/ext4/inline.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 1b094a4f3866..b48c7dbe76a2 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -418,7 +418,12 @@ static int ext4_prepare_inline_data(handle_t *handle, struct inode *inode, return -ENOSPC; ext4_write_lock_xattr(inode, &no_expand); - + /* + * ei->i_inline_size may have changed since the initial check + * if other xattrs were added. Recalculate to ensure + * ext4_update_inline_data() validates against current capacity. + */ + (void) ext4_find_inline_data_nolock(inode); if (ei->i_inline_off) ret = ext4_update_inline_data(handle, inode, len); else |