From: Rik van Riel Date: Mon, 6 Oct 2025 03:48:05 +0000 (-0400) Subject: x86/mm: Fix overflow in __cpa_addr() X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=f25785f9b088ed65089dd0d0034da52858417839;p=users%2Fhch%2Fmisc.git x86/mm: Fix overflow in __cpa_addr() The change to have cpa_flush() call flush_kernel_pages() introduced a bug where __cpa_addr() can access an address one larger than the largest one in the cpa->pages array. KASAN reports the issue like this: BUG: KASAN: slab-out-of-bounds in __cpa_addr arch/x86/mm/pat/set_memory.c:309 [inline] BUG: KASAN: slab-out-of-bounds in __cpa_addr+0x1d3/0x220 arch/x86/mm/pat/set_memory.c:306 Read of size 8 at addr ffff88801f75e8f8 by task syz.0.17/5978 This bug could cause cpa_flush() to not properly flush memory, which somehow never showed any symptoms in my tests, possibly because cpa_flush() is called so rarely, but could potentially cause issues for other people. Fix the issue by directly calculating the flush end address from the start address. Fixes: 86e6815b316e ("x86/mm: Change cpa_flush() to call flush_kernel_range() directly") Reported-by: syzbot+afec6555eef563c66c97@syzkaller.appspotmail.com Signed-off-by: Rik van Riel Signed-off-by: Dave Hansen Reviewed-by: Kiryl Shutsemau Link: https://lore.kernel.org/all/68e2ff90.050a0220.2c17c1.0038.GAE@google.com/ --- diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index d2d54b8c4dbb..970981893c9b 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -446,7 +446,7 @@ static void cpa_flush(struct cpa_data *cpa, int cache) } start = fix_addr(__cpa_addr(cpa, 0)); - end = fix_addr(__cpa_addr(cpa, cpa->numpages)); + end = start + cpa->numpages * PAGE_SIZE; if (cpa->force_flush_all) end = TLB_FLUSH_ALL;