| Message ID | 20210821035427.1471851-1-tytso@mit.edu |
|---|---|
| State | Accepted |
| Headers | show |
| Series | ext4: fix race writing to an inline_data file while its xattrs are changing | expand |
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git 9e445093e523f3277081314c864f708fd4bd34aa
Hello, syzbot has tested the proposed patch and the reproducer did not trigger any issue: Reported-and-tested-by: syzbot+13146364637c7363a7de@syzkaller.appspotmail.com Tested on: commit: 9e445093 ext4: fix race writing to an inline_data file.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git kernel config: https://syzkaller.appspot.com/x/.config?x=300aea483211c875 dashboard link: https://syzkaller.appspot.com/bug?extid=13146364637c7363a7de compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1 Note: testing is done by a robot and is best-effort only.
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 70cb64db33f7..24e994e75f5c 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -750,6 +750,12 @@ int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len, ext4_write_lock_xattr(inode, &no_expand); BUG_ON(!ext4_has_inline_data(inode)); + /* + * ei->i_inline_off may have changed since ext4_write_begin() + * called ext4_try_to_write_inline_data() + */ + (void) ext4_find_inline_data_nolock(inode); + kaddr = kmap_atomic(page); ext4_write_inline_data(inode, &iloc, kaddr, pos, len); kunmap_atomic(kaddr);
The location of the system.data extended attribute can change whenever xattr_sem is not taken. So we need to recalculate the i_inline_off field since it mgiht have changed between ext4_write_begin() and ext4_write_end(). This means that caching i_inline_off is probably not helpful, so in the long run we should probably get rid of it and shrink the in-memory ext4 inode slightly, but let's fix the race the simple way for now. Cc: stable@kernel.org Fixes: f19d5870cbf72 ("ext4: add normal write support for inline data") Reported-by: syzbot+13146364637c7363a7de@syzkaller.appspotmail.com Signed-off-by: Theodore Ts'o <tytso@mit.edu> --- fs/ext4/inline.c | 6 ++++++ 1 file changed, 6 insertions(+)