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>
---
Changes since v1:
* Add missing WARN_ON_ONCE().
* Correct the comment of alloc_flex_gd().
fs/ext4/resize.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index e04eb08b9060..a2704f064361 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -230,8 +230,8 @@ struct ext4_new_flex_group_data {
#define MAX_RESIZE_BG 16384
/*
- * alloc_flex_gd() allocates a ext4_new_flex_group_data with size of
- * @flexbg_size.
+ * alloc_flex_gd() allocates an ext4_new_flex_group_data that satisfies the
+ * resizing from @o_group to @n_group, its size is typically @flexbg_size.
*
* Returns NULL on failure otherwise address of the allocated structure.
*/
@@ -239,25 +239,27 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,
ext4_group_t o_group, ext4_group_t n_group)
{
ext4_group_t last_group;
+ unsigned int max_resize_bg;
struct ext4_new_flex_group_data *flex_gd;
flex_gd = kmalloc(sizeof(*flex_gd), GFP_NOFS);
if (flex_gd == NULL)
goto out3;
- if (unlikely(flexbg_size > MAX_RESIZE_BG))
- flex_gd->resize_bg = MAX_RESIZE_BG;
- else
- flex_gd->resize_bg = flexbg_size;
+ max_resize_bg = umin(flexbg_size, MAX_RESIZE_BG);
+ flex_gd->resize_bg = max_resize_bg;
/* 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));
+ if (WARN_ON_ONCE(flex_gd->resize_bg > max_resize_bg))
+ flex_gd->resize_bg = max_resize_bg;
+
flex_gd->groups = kmalloc_array(flex_gd->resize_bg,
sizeof(struct ext4_new_group_data),
GFP_NOFS);
--
2.39.2
