From: Yuanzheng Song songyuanzheng@huawei.com
The vma->anon_vma of the child process may be NULL because the entire vma does not contain anonymous pages. In this case, a BUG will occur when the copy_present_page() passes a copy of a non-anonymous page of that vma to the page_add_new_anon_rmap() to set up new anonymous rmap.
------------[ cut here ]------------ kernel BUG at mm/rmap.c:1052! Internal error: Oops - BUG: 0 [#1] SMP Modules linked in: CPU: 4 PID: 4652 Comm: test Not tainted 5.15.75 #1 Hardware name: linux,dummy-virt (DT) pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : __page_set_anon_rmap+0xc0/0xe8 lr : __page_set_anon_rmap+0xc0/0xe8 sp : ffff80000e773860 x29: ffff80000e773860 x28: fffffc13cf006ec0 x27: ffff04f3ccd68000 x26: ffff04f3c5c33248 x25: 0000000010100073 x24: ffff04f3c53c0a80 x23: 0000000020000000 x22: 0000000000000001 x21: 0000000020000000 x20: fffffc13cf006ec0 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 0000000000000000 x9 : ffffdddc5581377c x8 : 0000000000000000 x7 : 0000000000000011 x6 : ffff2717a8433000 x5 : ffff80000e773810 x4 : ffffdddc55400000 x3 : 0000000000000000 x2 : ffffdddc56b20000 x1 : ffff04f3c9a48040 x0 : 0000000000000000 Call trace: __page_set_anon_rmap+0xc0/0xe8 page_add_new_anon_rmap+0x13c/0x200 copy_pte_range+0x6b8/0x1018 copy_page_range+0x3a8/0x5e0 dup_mmap+0x3a0/0x6e8 dup_mm+0x78/0x140 copy_process+0x1528/0x1b08 kernel_clone+0xac/0x610 __do_sys_clone+0x78/0xb0 __arm64_sys_clone+0x30/0x40 invoke_syscall+0x68/0x170 el0_svc_common.constprop.0+0x80/0x250 do_el0_svc+0x48/0xb8 el0_svc+0x48/0x1a8 el0t_64_sync_handler+0xb0/0xb8 el0t_64_sync+0x1a0/0x1a4 Code: 97f899f4 f9400273 17ffffeb 97f899f1 (d4210000) ---[ end trace dc65e5edd0f362fa ]--- Kernel panic - not syncing: Oops - BUG: Fatal exception SMP: stopping secondary CPUs Kernel Offset: 0x5ddc4d400000 from 0xffff800008000000 PHYS_OFFSET: 0xfffffb0c80000000 CPU features: 0x44000cf1,00000806 Memory Limit: none ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]---
This problem has been fixed by the commit <fb3d824d1a46> ("mm/rmap: split page_dup_rmap() into page_dup_file_rmap() and page_try_dup_anon_rmap()"), but still exists in the linux-5.15.y branch.
This patch is not applicable to this version because of the large version differences. Therefore, fix it by adding non-anonymous page check in the copy_present_page().
Cc: stable@vger.kernel.org Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") Signed-off-by: Yuanzheng Song songyuanzheng@huawei.com Signed-off-by: Vlastimil Babka vbabka@suse.cz --- Hi, this was posted in [1] but seems stable@ was not actually included in the recipients. The 5.10 version [2] was applied as 935a8b62021 but 5.15 is missing.
[1] https://lore.kernel.org/all/20221028075244.3112566-1-songyuanzheng@huawei.co... [2] https://lore.kernel.org/all/20221028030705.2840539-1-songyuanzheng@huawei.co...
mm/memory.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c index 6d058973a97e..4785aecca9a8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -903,6 +903,17 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma if (likely(!page_needs_cow_for_dma(src_vma, page))) return 1;
+ /* + * The vma->anon_vma of the child process may be NULL + * because the entire vma does not contain anonymous pages. + * A BUG will occur when the copy_present_page() passes + * a copy of a non-anonymous page of that vma to the + * page_add_new_anon_rmap() to set up new anonymous rmap. + * Return 1 if the page is not an anonymous page. + */ + if (!PageAnon(page)) + return 1; + new_page = *prealloc; if (!new_page) return -EAGAIN;