Description

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

nilfs2: fix underflow in second superblock position calculations

Macro NILFS_SB2_OFFSET_BYTES, which computes the position of the second
superblock, underflows when the argument device size is less than 4096
bytes. Therefore, when using this macro, it is necessary to check in
advance that the device size is not less than a lower limit, or at least
that underflow does not occur.

The current nilfs2 implementation lacks this check, causing out-of-bound
block access when mounting devices smaller than 4096 bytes:

I/O error, dev loop0, sector 36028797018963960 op 0x0:(READ) flags 0x0
phys_seg 1 prio class 2
NILFS (loop0): unable to read secondary superblock (blocksize = 1024)

In addition, when trying to resize the filesystem to a size below 4096
bytes, this underflow occurs in nilfs_resize_fs(), passing a huge number
of segments to nilfs_sufile_resize(), corrupting parameters such as the
number of segments in superblocks. This causes excessive loop iterations
in nilfs_sufile_resize() during a subsequent resize ioctl, causing
semaphore ns_segctor_sem to block for a long time and hang the writer
thread:

INFO: task segctord:5067 blocked for more than 143 seconds.
Not tainted 6.2.0-rc8-syzkaller-00015-gf6feea56f66d #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:segctord state:D stack:23456 pid:5067 ppid:2
flags:0x00004000
Call Trace:

context_switc...

Classification

CVE ID: CVE-2023-52705

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.06% (scored less or equal to compared to others)

EPSS Date: 2025-02-03 (when was this score calculated)

References

https://git.kernel.org/stable/c/2f7a1135b202977b82457adde7db6c390056863b
https://git.kernel.org/stable/c/b96591e2c35c8b47db0ec816b5fc6cb8868000ff
https://git.kernel.org/stable/c/52844d8382cd9166d708032def8905ffc3ae550f
https://git.kernel.org/stable/c/0ee5ed0126a2211f7174492da2ca2c29f43755c5
https://git.kernel.org/stable/c/a158782b56b070485d54d25fc9aaf2c8f3752205
https://git.kernel.org/stable/c/a8ef5109f93cea9933bbac0455d8c18757b3fcb4
https://git.kernel.org/stable/c/99b9402a36f0799f25feee4465bfa4b8dfa74b4d

Timeline