The patch titled
Subject: mm/mprotect: Only reference swap pfn page if type match
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-mprotect-only-reference-swap-pfn-page-if-type-match.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mprotect-only-reference-swap-pfn-page-if-type-match.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm/mprotect: Only reference swap pfn page if type match
Date: Tue, 23 Aug 2022 18:11:38 -0400
Yu Zhao reported a bug after the commit "mm/swap: Add swp_offset_pfn() to
fetch PFN from swap entry" added a check in swp_offset_pfn() for swap type [1]:
kernel BUG at include/linux/swapops.h:117!
CPU: 46 PID: 5245 Comm: EventManager_De Tainted: G S O L 6.0.0-dbg-DEV #2
RIP: 0010:pfn_swap_entry_to_page+0x72/0xf0
Code: c6 48 8b 36 48 83 fe ff 74 53 48 01 d1 48 83 c1 08 48 8b 09 f6
c1 01 75 7b 66 90 48 89 c1 48 8b 09 f6 c1 01 74 74 5d c3 eb 9e <0f> 0b
48 ba ff ff ff ff 03 00 00 00 eb ae a9 ff 0f 00 00 75 13 48
RSP: 0018:ffffa59e73fabb80 EFLAGS: 00010282
RAX: 00000000ffffffe8 RBX: 0c00000000000000 RCX: ffffcd5440000000
RDX: 1ffffffffff7a80a RSI: 0000000000000000 RDI: 0c0000000000042b
RBP: ffffa59e73fabb80 R08: ffff9965ca6e8bb8 R09: 0000000000000000
R10: ffffffffa5a2f62d R11: 0000030b372e9fff R12: ffff997b79db5738
R13: 000000000000042b R14: 0c0000000000042b R15: 1ffffffffff7a80a
FS: 00007f549d1bb700(0000) GS:ffff99d3cf680000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000440d035b3180 CR3: 0000002243176004 CR4: 00000000003706e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
change_pte_range+0x36e/0x880
change_p4d_range+0x2e8/0x670
change_protection_range+0x14e/0x2c0
mprotect_fixup+0x1ee/0x330
do_mprotect_pkey+0x34c/0x440
__x64_sys_mprotect+0x1d/0x30
It triggers because pfn_swap_entry_to_page() could be called upon e.g. a
genuine swap entry.
Fix it by only calling it when it's a write migration entry where the page*
is used.
[1] https://lore.kernel.org/lkml/CAOUHufaVC2Za-p8m0aiHw6YkheDcrO-C3wRGixwDS32VTS+k1w@xxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20220823221138.45602-1-peterx@xxxxxxxxxx
Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive")
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reported-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Tested-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mprotect.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/mprotect.c~mm-mprotect-only-reference-swap-pfn-page-if-type-match
+++ a/mm/mprotect.c
@@ -196,10 +196,11 @@ static unsigned long change_pte_range(st
pages++;
} else if (is_swap_pte(oldpte)) {
swp_entry_t entry = pte_to_swp_entry(oldpte);
- struct page *page = pfn_swap_entry_to_page(entry);
pte_t newpte;
if (is_writable_migration_entry(entry)) {
+ struct page *page = pfn_swap_entry_to_page(entry);
+
/*
* A protection check is difficult so
* just be safe and disable write
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-mprotect-only-reference-swap-pfn-page-if-type-match.patch
mm-x86-use-swp_type_bits-in-3-level-swap-macros.patch
mm-swap-comment-all-the-ifdef-in-swapopsh.patch
mm-swap-add-swp_offset_pfn-to-fetch-pfn-from-swap-entry.patch
mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.patch
mm-remember-young-dirty-bit-for-page-migrations.patch
mm-swap-cache-maximum-swapfile-size-when-init-swap.patch
mm-swap-cache-swap-migration-a-d-bits-support.patch
