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Message-ID: <20240104102700.kqfc6xg3mc7ur5kl@quack3> Date: Thu, 4 Jan 2024 11:27:00 +0100 From: Jan Kara <jack@...e.cz> To: Baokun Li <libaokun1@...wei.com> Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com, linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com, yukuai3@...wei.com, Wei Chen <harperchen1110@...il.com>, xingwei lee <xrivendell7@...il.com>, stable@...r.kernel.org Subject: Re: [PATCH v2 1/8] ext4: fix double-free of blocks due to wrong extents moved_len On Thu 21-12-23 23:05:51, Baokun Li wrote: > In ext4_move_extents(), moved_len is only updated when all moves are > successfully executed, and only discards orig_inode and donor_inode > preallocations when moved_len is not zero. When the loop fails to exit > after successfully moving some extents, moved_len is not updated and > remains at 0, so it does not discard the preallocations. > > If the moved extents overlap with the preallocated extents, the > overlapped extents are freed twice in ext4_mb_release_inode_pa() and > ext4_process_freed_data() (as described in commit 94d7c16cbbbd ("ext4: > Fix double-free of blocks with EXT4_IOC_MOVE_EXT")), and bb_free is > incremented twice. Hence when trim is executed, a zero-division bug is > triggered in mb_update_avg_fragment_size() because bb_free is not zero > and bb_fragments is zero. > > Therefore, update move_len after each extent move to avoid the issue. > > Reported-by: Wei Chen <harperchen1110@...il.com> > Reported-by: xingwei lee <xrivendell7@...il.com> > Closes: https://lore.kernel.org/r/CAO4mrferzqBUnCag8R3m2zf897ts9UEuhjFQGPtODT92rYyR2Q@mail.gmail.com > Fixes: fcf6b1b729bc ("ext4: refactor ext4_move_extents code base") > CC: stable@...r.kernel.org # 3.18 > Signed-off-by: Baokun Li <libaokun1@...wei.com> Looks good! Feel free to add: Reviewed-by: Jan Kara <jack@...e.cz> Honza > --- > fs/ext4/move_extent.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c > index 3aa57376d9c2..391efa6d4c56 100644 > --- a/fs/ext4/move_extent.c > +++ b/fs/ext4/move_extent.c > @@ -618,6 +618,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk, > goto out; > o_end = o_start + len; > > + *moved_len = 0; > while (o_start < o_end) { > struct ext4_extent *ex; > ext4_lblk_t cur_blk, next_blk; > @@ -672,7 +673,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk, > */ > ext4_double_up_write_data_sem(orig_inode, donor_inode); > /* Swap original branches with new branches */ > - move_extent_per_page(o_filp, donor_inode, > + *moved_len += move_extent_per_page(o_filp, donor_inode, > orig_page_index, donor_page_index, > offset_in_page, cur_len, > unwritten, &ret); > @@ -682,9 +683,6 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk, > o_start += cur_len; > d_start += cur_len; > } > - *moved_len = o_start - orig_blk; > - if (*moved_len > len) > - *moved_len = len; > > out: > if (*moved_len) { > -- > 2.31.1 > -- Jan Kara <jack@...e.com> SUSE Labs, CR
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