On Fri, Sep 27, 2024 at 8:39 AM <libaokun@xxxxxxxxxxxxxxx> wrote: > > From: Baokun Li <libaokun1@xxxxxxxxxx> > > Wesley reported an issue: > > ================================================================== > EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks > ------------[ cut here ]------------ > kernel BUG at fs/ext4/resize.c:324! > CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27 > RIP: 0010:ext4_resize_fs+0x1212/0x12d0 > Call Trace: > __ext4_ioctl+0x4e0/0x1800 > ext4_ioctl+0x12/0x20 > __x64_sys_ioctl+0x99/0xd0 > x64_sys_call+0x1206/0x20d0 > do_syscall_64+0x72/0x110 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > ================================================================== > > While reviewing the patch, Honza found that when adjusting resize_bg in > alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than > flexbg_size. > > The reproduction of the problem requires the following: > > o_group = flexbg_size * 2 * n; > o_size = (o_group + 1) * group_size; > n_group: [o_group + flexbg_size, o_group + flexbg_size * 2) > o_size = (n_group + 1) * group_size; > > Take n=0,flexbg_size=16 as an example: > > last:15 > |o---------------|--------------n-| > o_group:0 resize to n_group:30 > > The corresponding reproducer is: > > img=test.img > truncate -s 600M $img > mkfs.ext4 -F $img -b 1024 -G 16 8M > dev=`losetup -f --show $img` > mkdir -p /tmp/test > mount $dev /tmp/test > resize2fs $dev 248M > > Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE() > to prevent the issue from happening again. > > Reported-by: Wesley Hershberger <wesley.hershberger@xxxxxxxxxxxxx> > Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231 > Reported-by: Stéphane Graber <stgraber@xxxxxxxxxxxx> > Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@xxxxxxxxxxxxx/ > Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> > Tested-by: Eric Sandeen <sandeen@xxxxxxxxxx> > Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()") > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx> Thanks, Baokun! JFYI, I'm on the way to submit a test to xfstests suite. Kind regards, Alex > --- > fs/ext4/resize.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c > index e04eb08b9060..397970121d43 100644 > --- a/fs/ext4/resize.c > +++ b/fs/ext4/resize.c > @@ -253,9 +253,9 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size, > /* Avoid allocating large 'groups' array if not needed */ > last_group = o_group | (flex_gd->resize_bg - 1); > if (n_group <= last_group) > - flex_gd->resize_bg = 1 << fls(n_group - o_group + 1); > + flex_gd->resize_bg = 1 << fls(n_group - o_group); > else if (n_group - last_group < flex_gd->resize_bg) > - flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1), > + flex_gd->resize_bg = 1 << max(fls(last_group - o_group), > fls(n_group - last_group)); > > flex_gd->groups = kmalloc_array(flex_gd->resize_bg, > -- > 2.46.0 >
