BaseFortify

Publication date: 2025-10-01

Last updated on: 2026-04-06

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: nbd: fix incomplete validation of ioctl arg We tested and found an alarm caused by nbd_ioctl arg without verification. The UBSAN warning calltrace like below: UBSAN: Undefined behaviour in fs/buffer.c:1709:35 signed integer overflow: -9223372036854775808 - 1 cannot be represented in type 'long long int' CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78 show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158 __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x170/0x1dc lib/dump_stack.c:118 ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161 handle_overflow+0x188/0x1dc lib/ubsan.c:192 __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206 __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709 block_write_full_page+0x1f0/0x280 fs/buffer.c:2934 blkdev_writepage+0x34/0x40 fs/block_dev.c:607 __writepage+0x68/0xe8 mm/page-writeback.c:2305 write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240 generic_writepages+0xdc/0x148 mm/page-writeback.c:2329 blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114 do_writepages+0xd4/0x250 mm/page-writeback.c:2344 The reason for triggering this warning is __block_write_full_page() -> i_size_read(inode) - 1 overflow. inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> bytesize. We think it is necessary to limit the size of arg to prevent errors. Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int. Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine), it will become 1 after the coercion, which will return unexpected results. Fix it by adding checks to prevent passing in too large numbers.

CVSS Scores

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Meta Information

Published

2025-10-01

Last Modified

2026-04-06

Generated

2026-07-07

AI Q&A

2025-10-01

EPSS Evaluated

2026-07-06

NVD

CVE-2023-53513

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	From 5.15.160 (inc) to 5.16 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel's nbd (network block device) subsystem involves incomplete validation of an ioctl argument. Specifically, the argument passed to nbd_ioctl can be too large, causing signed integer overflow and unexpected behavior when the argument is cast to a smaller integer type. This can lead to undefined behavior and potential errors in kernel operations related to block device writes.

Impact Analysis

The vulnerability can cause kernel errors due to integer overflow when handling certain ioctl arguments in the nbd subsystem. This may lead to unexpected results or instability in the system's block device operations, potentially affecting system reliability or causing crashes.

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