CVE-2026-89557: md: do overflow check for sb->bblog_shift in super_1_load()
In the Linux kernel, the following vulnerability has been resolved:
md: do overflow check for sb->bblogshift in super1load()
In super1load(), sb->bblogshift is an u8 type value loaded from on- disk superblock. It is used for badblocks API badblocksset() by the following sequence,
1930 rdev->badblocks.shift = sb->bblogshift; 1931 for (i = 0 ; i < (sectors << (9-3)) ; i++, bbp++) { 1932 u64 bb = le64tocpu(bbp); 1933 int count = bb & (0x3ff); 1934 u64 sector = bb >> 10; 1935 sector <<= sb->bblogshift; 1936 count <<= sb->bblogshift; 1937 if (bb + 1 == 0) 1938 break; 1939 if (!badblocksset(&rdev->badblocks, sector, count, 1)) 1940 return -EINVAL; 1941 }
bb->bblogshit is in range of 0-255, variable sector is 64bit width, for an invalid bb->bblogshit, it is possible to make sector be overflowed by the following calculation, 1935 sector <<= sb->bblogshift; Then in turn when call badblocksset() at line 1939 with the invalid rdev->badblocks.shift set at line 1930, may result an overflow inside badblocksclear() in block/badblocks.c.
Although there are many places to call badblocks APIs, the non-zero shift value is only used in super1load(), other places always use 0 as the shift value. Therefore it is unnecessary to do a general shift value overflow check inside badblock API, and just check here as the caller.
This may avoid unnecessary check, make the badblocks API code more simple and elegant.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.113-1~deb12u1 - Upgrade
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1119.126~20.04.1 - Upgrade
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ubuntu/linux-azure-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1125.134~20.04.1 - Upgrade
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ubuntu/linux-gcp-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1120.130~20.04.1 - Upgrade
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ubuntu/linux-hwe-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-202.212~20.04.1 - Upgrade
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ubuntu/linux-nvidia-tegra-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1070.72~20.04.1 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1119.126 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1125.134 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1120.130 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
What condition triggers the vulnerable path?
The path is reached when super_1_load() reads sb->bblog_shift from an on-disk superblock and uses it to shift bad-block sector and count values. An invalid shift value can overflow the 64-bit sector calculation and can subsequently cause an overflow in _badblocks_clear() through badblocks_set().
Is this behavior used by other badblocks API callers?
The description states that non-zero badblocks shift values are only used in super_1_load(). Other callers of the badblocks APIs use a shift value of zero.