In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
mm\/hugetlb_cma: fix null nodemask dereference in hugetlb_cma_alloc_frozen_folio<\/p>\n
alloc_buddy_hugetlb_folio_with_mpol() can pass a NULL nodemask to
\nalloc_fresh_hugetlb_folio() as a fallback to allocate from all nodes. If
\norder is gigantic, alloc_fresh_hugetlb_folio() propagates the NULL
\nnodemask down to hugetlb_cma_alloc_frozen_folio() via
\nalloc_gigantic_frozen_folio().<\/p>\n
Additionally, hugetlb_cma_alloc_frozen_folio() previously attempted
\nallocation on hugetlb_cma[nid] without verifying if nid is included in the
\ncaller’s nodemask. Adding a node_isset(nid, *nodemask) check ensures the
\ninitial preferred node allocation honors the memory policy \/ nodemask.<\/p>\n
However, hugetlb_cma_alloc_frozen_folio() dereferences the nodemask in
\nnode_isset(nid, *nodemask) and for_each_node_mask(node, *nodemask),
\nleading to a null pointer dereference kernel panic when nodemask is NULL.<\/p>\n
Fix this by checking if nodemask is NULL in
\nhugetlb_cma_alloc_frozen_folio() and defaulting it to
\ncpuset_current_mems_allowed. Enclose the allocation attempts within the
\ncpuset seqcount retry loop so that if the cpuset changes concurrently
\nduring allocation, the attempts are retried using the updated nodemask.
\nThis ensures that the initial node check and fallback loop safely honor
\nthe task’s cpuset without violating cpuset constraints or causing NULL
\npointer dereferences or unexpected allocation failures.<\/p>\n
From a userspace perspective, this bug allows an unprivileged user to
\ncrash the kernel (trigger a panic) by requesting a gigantic hugepage
\nallocation with MPOL_PREFERRED_MANY on a system where CMA is only
\nconfigured on a subset of NUMA nodes.<\/p>\n
This can be reproduced by booting a VM with two NUMA nodes, restricting
\nCMA to Node 1 (e.g., hugetlb_cma=1:1G default_hugepagesz=1G hugepagesz=1G
\nhugepages=0), and running a program that allocates a 1GB hugepage area
\nwithout reserving, restricts allocation to Node 0 using mbind() with
\nMPOL_PREFERRED_MANY, and triggers a page fault:<\/p>\n
void *ptr = mmap(NULL, 1UL << 30, PROT_READ | PROT_WRITE,
\n MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB |
\n MAP_HUGE_1GB | MAP_NORESERVE, -1, 0);
\n unsigned long nodemask = 1; \/* Node 0 *\/
\n mbind(ptr, 1UL << 30, MPOL_PREFERRED_MANY, &nodemask,
\n sizeof(nodemask) * 8, 0);
\n memset(ptr, 0, 1UL << 30); \/* Trigger fault *\/<\/p>\n
This results in a NULL pointer dereference:<\/p>\n
BUG: kernel NULL pointer dereference, address: 0000000000000000
\n #PF: supervisor read access in kernel mode
\n #PF: error_code(0x0000) – not-present page
\n Oops: Oops: 0000 [#1] SMP NOPTI
\n RIP: 0010:hugetlb_cma_alloc_frozen_folio+0x75\/0x120
\n Call Trace:<\/p>\n
only_alloc_fresh_hugetlb_folio.isra.0+0x2c\/0x160
\n alloc_surplus_hugetlb_folio+0x6d\/0x100
\n alloc_hugetlb_folio+0x3c5\/0x660
\n hugetlb_no_page+0x3d9\/0x650<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
mm\/hugetlb_cma: fix null nodemask dereference in hugetlb_cma_alloc_frozen_folio<\/p>\n
alloc_buddy_hugetlb_folio_with_mpol() can pass a N<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-24653","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/24653","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=24653"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=24653"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=24653"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}