Описание
In the Linux kernel, the following vulnerability has been resolved:
riscv: lib: Fix ZBB strnlen reading past count boundary
The ZBB-optimized strnlen loop loads one word ahead before checking the
aligned boundary:
REG_L t1, SZREG(t0) // load next word
addi t0, t0, SZREG // advance
orc.b t1, t1
bgeu t0, t4, 4f // boundary check AFTER load
where t4 = (s + count) & -SZREG. When s is aligned and count is a
multiple of SZREG, t4 equals s + count and the loop loads a full word
starting at exactly s + count. If s + count falls on a page boundary
with the next page unmapped, this faults.
Fix by computing the aligned boundary from the last valid byte
(s + count - 1) instead of s + count. This makes the loop stop at the
word containing the last valid byte rather than potentially loading the
word after it. The count == 0 case is already handled by the beqz
early exit.
Also add a pre-loop guard (bgeu t0, t4) for the case where all valid
bytes fit within the first word. With the adjusted boundary, t4 can
equal t0, and entering the loop with stale register state from the
first-word processing would produce incorrect results.
The final minu clamp ensures the result is still correct when the last
loaded word extends past s + count - 1 within the same aligned word.
A flaw was found in the Linux kernel's RISC-V (Reduced Instruction Set Computer - V) ZBB-optimized strnlen function. This vulnerability occurs because the strnlen loop attempts to read one word beyond the intended boundary. If the read operation crosses an unmapped memory page, it can lead to a system fault, resulting in a denial of service (DoS) for the affected system.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Not affected | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: riscv: lib: Fix ZBB strnlen reading past count boundary The ZBB-optimized strnlen loop loads one word ahead before checking the aligned boundary: REG_L t1, SZREG(t0) // load next word addi t0, t0, SZREG // advance orc.b t1, t1 bgeu t0, t4, 4f // boundary check AFTER load where t4 = (s + count) & -SZREG. When s is aligned and count is a multiple of SZREG, t4 equals s + count and the loop loads a full word starting at exactly s + count. If s + count falls on a page boundary with the next page unmapped, this faults. Fix by computing the aligned boundary from the last valid byte (s + count - 1) instead of s + count. This makes the loop stop at the word containing the last valid byte rather than potentially loading the word after it. The count == 0 case is already handled by the beqz early exit. Also add a pre-loop guard (bgeu t0, t4) for the case where all valid bytes fit within the fi...
In the Linux kernel, the following vulnerability has been resolved: riscv: lib: Fix ZBB strnlen reading past count boundary The ZBB-optimized strnlen loop loads one word ahead before checking the aligned boundary: REG_L t1, SZREG(t0) // load next word addi t0, t0, SZREG // advance orc.b t1, t1 bgeu t0, t4, 4f // boundary check AFTER load where t4 = (s + count) & -SZREG. When s is aligned and count is a multiple of SZREG, t4 equals s + count and the loop loads a full word starting at exactly s + count. If s + count falls on a page boundary with the next page unmapped, this faults. Fix by computing the aligned boundary from the last valid byte (s + count - 1) instead of s + count. This makes the loop stop at the word containing the last valid byte rather than potentially loading the word after it. The count == 0 case is already handled by the beqz early exit. Also add a pre-loop guard (bgeu t0, t4) for the case where all valid byte
In the Linux kernel, the following vulnerability has been resolved: r ...
In the Linux kernel, the following vulnerability has been resolved: riscv: lib: Fix ZBB strnlen reading past count boundary The ZBB-optimized strnlen loop loads one word ahead before checking the aligned boundary: REG_L t1, SZREG(t0) // load next word addi t0, t0, SZREG // advance orc.b t1, t1 bgeu t0, t4, 4f // boundary check AFTER load where t4 = (s + count) & -SZREG. When s is aligned and count is a multiple of SZREG, t4 equals s + count and the loop loads a full word starting at exactly s + count. If s + count falls on a page boundary with the next page unmapped, this faults. Fix by computing the aligned boundary from the last valid byte (s + count - 1) instead of s + count. This makes the loop stop at the word containing the last valid byte rather than potentially loading the word after it. The count == 0 case is already handled by the beqz early exit. Also add a pre-loop guard (bgeu t0, t4) for the case where all valid b...
EPSS
5.5 Medium
CVSS3