From c5ca8e1795a1a50a23062459fa4dedb04f581665 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Fri, 20 Aug 2021 23:44:17 -0400 Subject: [PATCH] ext4: fix race writing to an inline_data file while its xattrs are changing 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: d0a39f0ee631b ("ext4: add normal write support for inline data") Reported-by: syzbot+13146364637c7363a7de@syzkaller.appspotmail.com Signed-off-by: Theodore Ts'o --- fs/ext4/inline.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 70cb64db33f73..24e994e75f5ca 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); -- 2.39.5