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authorQi Zheng <zhengqi.arch@bytedance.com>2022-07-26 14:24:36 +0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-07-26 09:21:43 -0700
commitcdb281e63874086a650552d36c504ea717a0e0cb (patch)
tree22d312d4d3875c486bdd61311d36a116fada06be /mm
parente0dccc3b76fb35bb257b4118367a883073d7390e (diff)
mm: fix NULL pointer dereference in wp_page_reuse()
The vmf->page can be NULL when the wp_page_reuse() is invoked by wp_pfn_shared(), it will cause the following panic: BUG: kernel NULL pointer dereference, address: 000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 18 PID: 923 Comm: Xorg Not tainted 5.19.0-rc8.bm.1-amd64 #263 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g14 RIP: 0010:_compound_head+0x0/0x40 [...] Call Trace: wp_page_reuse+0x1c/0xa0 do_wp_page+0x1a5/0x3f0 __handle_mm_fault+0x8cf/0xd20 handle_mm_fault+0xd5/0x2a0 do_user_addr_fault+0x1d0/0x680 exc_page_fault+0x78/0x170 asm_exc_page_fault+0x22/0x30 To fix it, this patch performs a NULL pointer check before dereferencing the vmf->page. Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive") Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memory.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 4cf7d4b6c950..9174918ce3f7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3043,7 +3043,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
pte_t entry;
VM_BUG_ON(!(vmf->flags & FAULT_FLAG_WRITE));
- VM_BUG_ON(PageAnon(page) && !PageAnonExclusive(page));
+ VM_BUG_ON(page && PageAnon(page) && !PageAnonExclusive(page));
/*
* Clear the pages cpupid information as the existing