From: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com
A KASAN tag mismatch, possibly causing a kernel panic, can be observed on systems with a tag-based KASAN enabled and with multiple NUMA nodes. It was reported on arm64 and reproduced on x86. It can be explained in the following points:
1. There can be more than one virtual memory chunk. 2. Chunk's base address has a tag. 3. The base address points at the first chunk and thus inherits the tag of the first chunk. 4. The subsequent chunks will be accessed with the tag from the first chunk. 5. Thus, the subsequent chunks need to have their tag set to match that of the first chunk.
Use the new vmalloc flag that disables random tag assignment in __kasan_unpoison_vmalloc() - pass the same random tag to all the vm_structs by tagging the pointers before they go inside __kasan_unpoison_vmalloc(). Assigning a common tag resolves the pcpu chunk address mismatch.
Fixes: 1d96320f8d53 ("kasan, vmalloc: add vmalloc tagging for SW_TAGS") Cc: stable@vger.kernel.org # 6.1+ Reviewed-by: Andrey Konovalov andreyknvl@gmail.com Signed-off-by: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com --- Changelog v4: - Add WARN_ON_ONCE() if the new flag is already set in the helper. (Andrey) - Remove pr_warn() since the comment should be enough. (Andrey)
Changelog v3: - Redo the patch by using a flag instead of a new argument in __kasan_unpoison_vmalloc() (Andrey Konovalov)
Changelog v2: - Revise the whole patch to match the fixed refactorization from the first patch.
Changelog v1: - Rewrite the patch message to point at the user impact of the issue. - Move helper to common.c so it can be compiled in all KASAN modes.
mm/kasan/common.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/mm/kasan/common.c b/mm/kasan/common.c index b2b40c59ce18..ed489a14dddf 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -584,11 +584,26 @@ void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms, unsigned long size; void *addr; int area; + u8 tag; + + /* + * If KASAN_VMALLOC_KEEP_TAG was set at this point, all vms[] pointers + * would be unpoisoned with the KASAN_TAG_KERNEL which would disable + * KASAN checks down the line. + */ + if (WARN_ON_ONCE(flags & KASAN_VMALLOC_KEEP_TAG)) + return; + + size = vms[0]->size; + addr = vms[0]->addr; + vms[0]->addr = __kasan_unpoison_vmalloc(addr, size, flags); + tag = get_tag(vms[0]->addr);
- for (area = 0 ; area < nr_vms ; area++) { + for (area = 1 ; area < nr_vms ; area++) { size = vms[area]->size; - addr = vms[area]->addr; - vms[area]->addr = __kasan_unpoison_vmalloc(addr, size, flags); + addr = set_tag(vms[area]->addr, tag); + vms[area]->addr = + __kasan_unpoison_vmalloc(addr, size, flags | KASAN_VMALLOC_KEEP_TAG); } } #endif