The patch titled Subject: nilfs2: fix possible out-of-bounds segment allocation in resize ioctl has been added to the -mm mm-hotfixes-unstable branch. Its filename is nilfs2-fix-possible-out-of-bounds-segment-allocation-in-resize-ioctl.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days

------------------------------------------------------ From: Ryusuke Konishi konishi.ryusuke@gmail.com Subject: nilfs2: fix possible out-of-bounds segment allocation in resize ioctl Date: Wed, 24 May 2023 18:43:48 +0900

Syzbot reports that in its stress test for resize ioctl, the log writing function nilfs_segctor_do_construct hits a WARN_ON in nilfs_segctor_truncate_segments().

It turned out that there is a problem with the current implementation of the resize ioctl, which changes the writable range on the device (the range of allocatable segments) at the end of the resize process.

This order is necessary for file system expansion to avoid corrupting the superblock at trailing edge. However, in the case of a file system shrink, if log writes occur after truncating out-of-bounds trailing segments and before the resize is complete, segments may be allocated from the truncated space.

The userspace resize tool was fine as it limits the range of allocatable segments before performing the resize, but it can run into this issue if the resize ioctl is called alone.

Fix this issue by changing nilfs_sufile_resize() to update the range of allocatable segments immediately after successful truncation of segment space in case of file system shrink.

Link: https://lkml.kernel.org/r/20230524094348.3784-1-konishi.ryusuke@gmail.com Fixes: 4e33f9eab07e ("nilfs2: implement resize ioctl") Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Reported-by: syzbot+33494cd0df2ec2931851@syzkaller.appspotmail.com Closes: https://lkml.kernel.org/r/0000000000005434c405fbbafdc5@google.com Tested-by: Ryusuke Konishi konishi.ryusuke@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/nilfs2/sufile.c | 9 +++++++++ 1 file changed, 9 insertions(+)

--- a/fs/nilfs2/sufile.c~nilfs2-fix-possible-out-of-bounds-segment-allocation-in-resize-ioctl +++ a/fs/nilfs2/sufile.c @@ -779,6 +779,15 @@ int nilfs_sufile_resize(struct inode *su goto out_header;

sui->ncleansegs -= nsegs - newnsegs; + + /* + * If the sufile is successfully truncated, immediately adjust + * the segment allocation space while locking the semaphore + * "mi_sem" so that nilfs_sufile_alloc() never allocates + * segments in the truncated space. + */ + sui->allocmax = newnsegs - 1; + sui->allocmin = 0; }

kaddr = kmap_atomic(header_bh->b_page); _

Patches currently in -mm which might be from konishi.ryusuke@gmail.com are

nilfs2-fix-incomplete-buffer-cleanup-in-nilfs_btnode_abort_change_key.patch nilfs2-fix-possible-out-of-bounds-segment-allocation-in-resize-ioctl.patch