On Fri, Sep 27, 2024 at 8:39 AM libaokun@huaweicloud.com wrote:
From: Baokun Li libaokun1@huawei.com
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@canonical.com Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231 Reported-by: Stéphane Graber stgraber@stgraber.org Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@ca... Tested-by: Alexander Mikhalitsyn aleksandr.mikhalitsyn@canonical.com Tested-by: Eric Sandeen sandeen@redhat.com Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()") Cc: stable@vger.kernel.org Signed-off-by: Baokun Li libaokun1@huawei.com
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