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If the gfp flags do not have __GFP_SKIP_KASAN, but the other mappings have PROT_MTE, we can end up with false KASAN errors such as BUG: KASAN: invalid-access in swap_writepage+0xb0/0x21c Read at addr f5ffff81aa71dff8 by task WM.task-4/6956 Pointer tag: [f5], memory tag: [f9] In the above example, because __GFP_SKIP_KASAN was missing, KASAN set both pointer tag and memory tag to 0xf5 when swap_cluster_readahead allocated the folio. But the userspace had already set the memory tag to 0xf9 before swapped out. arch_swap_restore restored the memory tag back to 0xf9, leading to the mismatch. Signed-off-by: Chia-I Wu --- Changes in v2: - set __GFP_SKIP_KASAN for shmem instead of drm/panthor - Link to v1: https://patch.msgid.link/20260512-panthor-kasan-v1-1-d8d3e275d71b@gmail.com --- mm/shmem.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index 3b5dc21b323c2..db9130a8c5b76 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1784,6 +1784,11 @@ static struct folio *shmem_swapin_cluster(swp_entry_t swap, gfp_t gfp, pgoff_t ilx; struct folio *folio; + /* swap_cluster_readahead might cross the mapping boundary and + * allocate pages for other mappings. We have to skip KASAN. + */ + gfp |= __GFP_SKIP_KASAN; + mpol = shmem_get_pgoff_policy(info, index, 0, &ilx); folio = swap_cluster_readahead(swap, gfp, mpol, ilx); mpol_cond_put(mpol); --- base-commit: 5200f5f493f79f14bbdc349e402a40dfb32f23c8 change-id: 20260512-panthor-kasan-10477239bad1 Best regards, -- Chia-I Wu