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CVE-2021-47649: udmabuf: validate ubuf->pagecount

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-02-26 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: udmabuf: validate ubuf->pagecount Syzbot has reported GPF in sg_alloc_append_table_from_pages(). The problem was in ubuf->pages == ZERO_PTR. ubuf->pagecount is calculated from arguments passed from user-space. If user creates udmabuf with list.size == 0 then ubuf->pagecount will be also equal to zero; it causes kmalloc_array() to return ZERO_PTR. Fix it by validating ubuf->pagecount before passing it to kmalloc_array().

Affected products

• Linux kernel: from 4.20 before 5.4.189; from 5.5 before 5.10.110; from 5.11 before 5.15.33; from 5.16 before 5.16.19; from 5.17 before 5.17.2 — fixed in 5.10.110, 5.15.33, 5.16.19, 5.17.2, 5.4.189

How to fix

Upgrade to a fixed version: Linux kernel 5.10.110, 5.15.33, 5.16.19, 5.17.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/2b6dd600dd72573c23ea180b5b0b2f1813405882
• https://git.kernel.org/stable/c/5d50f851dd307c07ca5591297093f19967c834a9
• https://git.kernel.org/stable/c/811b667cefbea9cb7511a874b169d6a92907137e
• https://git.kernel.org/stable/c/9e9b4a269f84d3230f2af84ff42322db676440d9
• https://git.kernel.org/stable/c/a3728d32fc61eb0fe283cb8ff60b2c8f751e2202
• https://git.kernel.org/stable/c/b267a8118c2b171bf7d67b90ed64154eeab9fae0

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