mm/filemap: make MAX_PAGECACHE_ORDER acceptable to xarray

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2024-42243
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-08-07 16:15:47 UTC
Updated2026-10-30 13:17:32 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: mm/filemap: make MAX_PAGECACHE_ORDER acceptable to xarray Patch series "mm/filemap: Limit page cache size to that supported by xarray", v2. Currently, xarray can't support arbitrary page cache size. More details can be found from the WARN_ON() statement in xas_split_alloc(). In our test whose code is attached below, we hit the WARN_ON() on ARM64 system where the base page size is 64KB and huge page size is 512MB. The issue was reported long time ago and some discussions on it can be found here [1]. [1] https://www.spinics.net/lists/linux-xfs/msg75404.html In order to fix the issue, we need to adjust MAX_PAGECACHE_ORDER to one supported by xarray and avoid PMD-sized page cache if needed. The code changes are suggested by David Hildenbrand. PATCH[1] adjusts MAX_PAGECACHE_ORDER to that supported by xarray PATCH[2-3] avoids PMD-sized page cache in the synchronous readahead path PATCH[4] avoids PMD-sized page cache for shmem files if needed Test program ============ # cat test.c #define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <fcntl.h> #include <errno.h> #include <sys/syscall.h> #include <sys/mman.h> #define TEST_XFS_FILENAME "/tmp/data" #define TEST_SHMEM_FILENAME "/dev/shm/data" #define TEST_MEM_SIZE 0x20000000 int main(int argc, char **argv) { const char *filename; int fd = 0; void *buf = (void *)-1, *p; int pgsize = getpagesize(); int ret; if (pgsize != 0x10000) { fprintf(stderr, "64KB base page size is required\n"); return -EPERM; } system("echo force > /sys/kernel/mm/transparent_hugepage/shmem_enabled"); system("rm -fr /tmp/data"); system("rm -fr /dev/shm/data"); system("echo 1 > /proc/sys/vm/drop_caches"); /* Open xfs or shmem file */ filename = TEST_XFS_FILENAME; if (argc > 1 && !strcmp(argv[1], "shmem")) filename = TEST_SHMEM_FILENAME; fd = open(filename, O_CREAT | O_RDWR | O_TRUNC); if (fd < 0) { fprintf(stderr, "Unable to open <%s>\n", filename); return -EIO; } /* Extend file size */ ret = ftruncate(fd, TEST_MEM_SIZE); if (ret) { fprintf(stderr, "Error %d to ftruncate()\n", ret); goto cleanup; } /* Create VMA */ buf = mmap(NULL, TEST_MEM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if (buf == (void *)-1) { fprintf(stderr, "Unable to mmap <%s>\n", filename); goto cleanup; } fprintf(stdout, "mapped buffer at 0x%p\n", buf); ret = madvise(buf, TEST_MEM_SIZE, MADV_HUGEPAGE); if (ret) { fprintf(stderr, "Unable to madvise(MADV_HUGEPAGE)\n"); goto cleanup; } /* Populate VMA */ ret = madvise(buf, TEST_MEM_SIZE, MADV_POPULATE_WRITE); if (ret) { fprintf(stderr, "Error %d to madvise(MADV_POPULATE_WRITE)\n", ret); goto cleanup; } /* Punch the file to enforce xarray split */ ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, TEST_MEM_SIZE - pgsize, pgsize); if (ret) fprintf(stderr, "Error %d to fallocate()\n", ret); cleanup: if (buf != (void *)-1) munmap(buf, TEST_MEM_SIZE); if (fd > 0) close(fd); return 0; } # gcc test.c -o test # cat /proc/1/smaps | grep KernelPageSize | head -n 1 KernelPageSize: 64 kB # ./test shmem : ------------[ cut here ]------------ WARNING: CPU: 17 PID: 5253 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128 Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib \ nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct \ nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 \ ip_set nf_tables rfkill nfnetlink vfat fat virtio_balloon \ drm fuse xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 \ virtio_net sha1_ce net_failover failover virtio_console virtio_blk \ dimlib virtio_mmio CPU: 17 PID: 5253 Comm: test Kdump: loaded Tainted: G W 6.10.0-rc5-gavin+ #12 Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/2024 pstate: 83400005 (Nzcv daif +PAN -UAO +TC ---truncated---

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 793917d997df2e432f3e9ac126e4482d68256d01 0c8a837153c15c33f9b4616860331a2dba1120c1 git Not specified
CNA Linux Linux affected 793917d997df2e432f3e9ac126e4482d68256d01 a0c42ddd0969fdc760a85e20e267776028a7ca4e git Not specified
CNA Linux Linux affected 793917d997df2e432f3e9ac126e4482d68256d01 333c5539a31f48828456aa9997ec2808f06a699a git Not specified
CNA Linux Linux affected 793917d997df2e432f3e9ac126e4482d68256d01 099d90642a711caae377f53309abfe27e8724a8b git Not specified
CNA Linux Linux affected 5.18 Not specified
CNA Linux Linux unaffected 5.18 semver Not specified
CNA Linux Linux unaffected 6.1.191 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.41 6.6.* semver Not specified
CNA Linux Linux unaffected 6.9.10 6.9.* semver Not specified
CNA Linux Linux unaffected 6.10 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/099d90642a711caae377f53309abfe27e8724a8b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/0c8a837153c15c33f9b4616860331a2dba1120c1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a0c42ddd0969fdc760a85e20e267776028a7ca4e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/333c5539a31f48828456aa9997ec2808f06a699a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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