CVE-2021-47007: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix panic during f2fs_resize_fs() f2fs_resize_fs() hangs in below callstack with testcase: - mkfs 16GB image & mount image - dd 8GB fileA - dd 8GB fileB - sync - rm fileA - sync - resize filesystem to 8GB kernel BUG at segment.c:2484! Call Trace: allocate_segment_by_default+0x92/0xf0 [f2fs] f2fs_allocate_data_block+0x44b/0x7e0 [f2fs] do_write_page+0x5a/0x110 [f2fs] f2fs_outplace_write_data+0x55/0x100 [f2fs] f2fs_do_write_data_page+0x392/0x850 [f2fs] move_data_page+0x233/0x320 [f2fs] do_garbage_collect+0x14d9/0x1660 [f2fs] free_segment_range+0x1f7/0x310 [f2fs] f2fs_resize_fs+0x118/0x330 [f2fs] __f2fs_ioctl+0x487/0x3680 [f2fs] __x64_sys_ioctl+0x8e/0xd0 do_syscall_64+0x33/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The root cause is we forgot to check that whether we have enough space in resized filesystem to store all valid blocks in before-resizing filesystem, then allocator will run out-of-space during block migration in free_segment_range().

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-754 CWE-754

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.8 — 5.10.38
linux	linux_kernel	5.11 — 5.11.22
linux	linux_kernel	5.12 — 5.12.5

References

Advisories & Patches

https://git.kernel.org/stable/c/1c20a4896409f5ca1c770e1880c33d0a28a8b10f https://git.kernel.org/stable/c/3ab0598e6d860ef49d029943ba80f627c15c15d6 https://git.kernel.org/stable/c/822054e5026c43b1dd60cf387dd999e95ee2ecc2 https://git.kernel.org/stable/c/860afd680d9cc1dabd61cda3cd246f60aa1eb705 https://git.kernel.org/stable/c/1c20a4896409f5ca1c770e1880c33d0a28a8b10f https://git.kernel.org/stable/c/3ab0598e6d860ef49d029943ba80f627c15c15d6 https://git.kernel.org/stable/c/822054e5026c43b1dd60cf387dd999e95ee2ecc2 https://git.kernel.org/stable/c/860afd680d9cc1dabd61cda3cd246f60aa1eb705

Frequently Asked Questions

What is CVE-2021-47007? +

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix panic during f2fs_resize_fs() f2fs_resize_fs() hangs in below callstack with testcase: - mkfs 16GB image & mount image - dd 8GB fileA - dd 8GB fileB - sync - rm fileA - sync - resize filesystem to 8GB kernel BUG at segment.c:2484! Call Trace: allocate_segment_by_default+0x92/0xf0 [f2fs] f2fs_allocate_data_block+0x44b/0x7e0 [f2fs] do_write_page+0x5a/0x110 [f2fs] f2fs_outplace_write_data+0x55/0x100 [f2fs] f2fs_do_write_data_page+0x392/0x850 [f2fs] move_data_page+0x233/0x320 [f2fs] do_garbage_collect+0x14d9/0x1660 [f2fs] free_segment_range+0x1f7/0x310 [f2fs] f2fs_resize_fs+0x118/0x330 [f2fs] __f2fs_ioctl+0x487/0x3680 [f2fs] __x64_sys_ioctl+0x8e/0xd0 do_syscall_64+0x33/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The root cause is we forgot to check that whether we have enough space in resized filesystem to store all valid blocks in before-resizing filesystem, then allocator will run out-of-space during block migration in free_segment_range(). It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47007? +

CVE-2021-47007 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2021-47007? +

CVE-2021-47007 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47007? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2021-47007