From 574a6db80f3eff7cb3a27aa92d126a69895a285d Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Mon, 13 Nov 2023 17:20:33 -0800 Subject: [PATCH] hugetlb: fix null-ptr-deref in hugetlb_vma_lock_write commit 187da0f8250aa94bd96266096aef6f694e0b4cd2 upstream. The routine __vma_private_lock tests for the existence of a reserve map associated with a private hugetlb mapping. A pointer to the reserve map is in vma->vm_private_data. __vma_private_lock was checking the pointer for NULL. However, it is possible that the low bits of the pointer could be used as flags. In such instances, vm_private_data is not NULL and not a valid pointer. This results in the null-ptr-deref reported by syzbot: general protection fault, probably for non-canonical address 0xdffffc000000001d: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef] CPU: 0 PID: 5048 Comm: syz-executor139 Not tainted 6.6.0-rc7-syzkaller-00142-g88 8cf78c29e2 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 1 0/09/2023 RIP: 0010:__lock_acquire+0x109/0x5de0 kernel/locking/lockdep.c:5004 ... Call Trace: lock_acquire kernel/locking/lockdep.c:5753 [inline] lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718 down_write+0x93/0x200 kernel/locking/rwsem.c:1573 hugetlb_vma_lock_write mm/hugetlb.c:300 [inline] hugetlb_vma_lock_write+0xae/0x100 mm/hugetlb.c:291 __hugetlb_zap_begin+0x1e9/0x2b0 mm/hugetlb.c:5447 hugetlb_zap_begin include/linux/hugetlb.h:258 [inline] unmap_vmas+0x2f4/0x470 mm/memory.c:1733 exit_mmap+0x1ad/0xa60 mm/mmap.c:3230 __mmput+0x12a/0x4d0 kernel/fork.c:1349 mmput+0x62/0x70 kernel/fork.c:1371 exit_mm kernel/exit.c:567 [inline] do_exit+0x9ad/0x2a20 kernel/exit.c:861 __do_sys_exit kernel/exit.c:991 [inline] __se_sys_exit kernel/exit.c:989 [inline] __x64_sys_exit+0x42/0x50 kernel/exit.c:989 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Mask off low bit flags before checking for NULL pointer. In addition, the reserve map only 'belongs' to the OWNER (parent in parent/child relationships) so also check for the OWNER flag. Link: https://lkml.kernel.org/r/20231114012033.259600-1-mike.kravetz@oracle.com Reported-by: syzbot+6ada951e7c0f7bc8a71e@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/00000000000078d1e00608d7878b@google.com/ Fixes: bf4916922c60 ("hugetlbfs: extend hugetlb_vma_lock to private VMAs") Signed-off-by: Mike Kravetz Reviewed-by: Rik van Riel Cc: Edward Adam Davis Cc: Muchun Song Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Tom Rix Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- include/linux/hugetlb.h | 5 +---- mm/hugetlb.c | 7 +++++++ 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index e46f6b49eb38..1c6f35ba1604 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -880,10 +880,7 @@ static inline bool hugepage_migration_supported(struct hstate *h) return arch_hugetlb_migration_supported(h); } -static inline bool __vma_private_lock(struct vm_area_struct *vma) -{ - return (!(vma->vm_flags & VM_MAYSHARE)) && vma->vm_private_data; -} +bool __vma_private_lock(struct vm_area_struct *vma); /* * Movability check is different as compared to migration check. diff --git a/mm/hugetlb.c b/mm/hugetlb.c index aa4a68dfb3b9..37288a7f0fa6 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1189,6 +1189,13 @@ static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag) return (get_vma_private_data(vma) & flag) != 0; } +bool __vma_private_lock(struct vm_area_struct *vma) +{ + return !(vma->vm_flags & VM_MAYSHARE) && + get_vma_private_data(vma) & ~HPAGE_RESV_MASK && + is_vma_resv_set(vma, HPAGE_RESV_OWNER); +} + void hugetlb_dup_vma_private(struct vm_area_struct *vma) { VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);