CVE intelligence and bounded remediation

CVE-2022-49049 — Linux Linux Kernel security vulnerability

In the Linux kernel, the following vulnerability has been resolved: mm/secretmem: fix panic when growing a memfd_secret When one tries to grow an existing memfd_secret with ftruncate, one gets a panic [1]. For example, doing the following reliably induces the panic: fd = memfd_secret(); ftruncate(fd, 10); ptr = mmap(NULL, 10, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); strcpy(ptr, "123456789"); munmap(ptr, 10); ftruncate(fd, 20); The basic reason for this is, when we grow with ftruncate, we call down into simple_setattr, and then truncate_inode_pages_range, and eventually we try to zero part of the memory. The normal truncation code does this via the direct map (i.e., it calls page_address() and hands that to memset()). For memfd_secret though, we specifically don't map our pages via the direct map (i.e. we call set_direct_map_invalid_noflush() on every fault). So the address returned by page_address() isn't useful, and when we try to memset() with it we panic. This patch avoids the panic by implementing a custom setattr for memfd_secret, which detects resizes specifically (setting the size for the first time works just fine, since there are no existing pages to try to zero), and…

Severity

Medium

CVSS

5.5 (3.1)

Published

2025-02-26

CISA KEV

Not currently listed

Ecosystem

linux/kernel