Vulnerability CVE-2023-52622

Vulnerability CVE-2023-52622

Published: 2024-03-26

Description:

In the Linux kernel, the following vulnerability has been resolved:

ext4: avoid online resizing failures due to oversized flex bg

When we online resize an ext4 filesystem with a oversized flexbg_size,

mkfs.ext4 -F -G 67108864 $dev -b 4096 100M
mount $dev $dir
resize2fs $dev 16G

the following WARN_ON is triggered:
==================================================================
WARNING: CPU: 0 PID: 427 at mm/page_alloc.c:4402 __alloc_pages+0x411/0x550
Modules linked in: sg(E)
CPU: 0 PID: 427 Comm: resize2fs Tainted: G E 6.6.0-rc5+ #314
RIP: 0010:__alloc_pages+0x411/0x550
Call Trace:
<TASK>
__kmalloc_large_node+0xa2/0x200
__kmalloc+0x16e/0x290
ext4_resize_fs+0x481/0xd80
__ext4_ioctl+0x1616/0x1d90
ext4_ioctl+0x12/0x20
__x64_sys_ioctl+0xf0/0x150
do_syscall_64+0x3b/0x90
==================================================================

This is because flexbg_size is too large and the size of the new_group_data
array to be allocated exceeds MAX_ORDER. Currently, the minimum value of
MAX_ORDER is 8, the minimum value of PAGE_SIZE is 4096, the corresponding
maximum number of groups that can be allocated is:

(PAGE_SIZE << MAX_ORDER) / sizeof(struct ext4_new_group_data) ? 21845

And the value that is down-aligned to the power of 2 is 16384. Therefore,
this value is defined as MAX_RESIZE_BG, and the number of groups added
each time does not exceed this value during resizing, and is added multiple
times to complete the online resizing. The difference is that the metadata
in a flex_bg may be more dispersed.

References:

https://git.kernel.org/stable/c/cd1f93ca97a9136989f3bd2bf90696732a2ed644

https://git.kernel.org/stable/c/b183fe8702e78bba3dcef8e7193cab6898abee07

https://git.kernel.org/stable/c/cfbbb3199e71b63fc26cee0ebff327c47128a1e8

https://git.kernel.org/stable/c/d76c8d7ffe163c6bf2f1ef680b0539c2b3902b90

https://git.kernel.org/stable/c/6d2cbf517dcabc093159cf138ad5712c9c7fa954

https://git.kernel.org/stable/c/8b1413dbfe49646eda2c00c0f1144ee9d3368e0c

https://git.kernel.org/stable/c/dc3e0f55bec4410f3d74352c4a7c79f518088ee2

https://git.kernel.org/stable/c/5d1935ac02ca5aee364a449a35e2977ea84509b0

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