The patch titled
Subject: mm: fix possible NULL pointer dereference in __swap_duplicate
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-fix-possible-null-pointer-dereference-in-__swap_duplicate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-possible-null-pointer-dereference-in-__swap_duplicate.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: gaoxu <gaoxu2@xxxxxxxxx>
Subject: mm: fix possible NULL pointer dereference in __swap_duplicate
Date: Wed, 19 Feb 2025 01:56:28 +0000
Add a NULL check on the return value of swp_swap_info in __swap_duplicate
to prevent crashes caused by NULL pointer dereference.
The reason why swp_swap_info() returns NULL is unclear; it may be due to
CPU cache issues or DDR bit flips. The probability of this issue is very
small, and the stack info we encountered is as follows:
Unable to handle kernel NULL pointer dereference at virtual address
0000000000000058
[RB/E]rb_sreason_str_set: sreason_str set null_pointer
Mem abort info:
ESR = 0x0000000096000005
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x05: level 1 translation fault
Data abort info:
ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 39-bit VAs, pgdp=00000008a80e5000
[0000000000000058] pgd=0000000000000000, p4d=0000000000000000,
pud=0000000000000000
Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
Skip md ftrace buffer dump for: 0x1609e0
...
pc : swap_duplicate+0x44/0x164
lr : copy_page_range+0x508/0x1e78
sp : ffffffc0f2a699e0
x29: ffffffc0f2a699e0 x28: ffffff8a5b28d388 x27: ffffff8b06603388
x26: ffffffdf7291fe70 x25: 0000000000000006 x24: 0000000000100073
x23: 00000000002d2d2f x22: 0000000000000008 x21: 0000000000000000
x20: 00000000002d2d2f x19: 18000000002d2d2f x18: ffffffdf726faec0
x17: 0000000000000000 x16: 0010000000000001 x15: 0040000000000001
x14: 0400000000000001 x13: ff7ffffffffffb7f x12: ffeffffffffffbff
x11: ffffff8a5c7e1898 x10: 0000000000000018 x9 : 0000000000000006
x8 : 1800000000000000 x7 : 0000000000000000 x6 : ffffff8057c01f10
x5 : 000000000000a318 x4 : 0000000000000000 x3 : 0000000000000000
x2 : 0000006daf200000 x1 : 0000000000000001 x0 : 18000000002d2d2f
Call trace:
swap_duplicate+0x44/0x164
copy_page_range+0x508/0x1e78
copy_process+0x1278/0x21cc
kernel_clone+0x90/0x438
__arm64_sys_clone+0x5c/0x8c
invoke_syscall+0x58/0x110
do_el0_svc+0x8c/0xe0
el0_svc+0x38/0x9c
el0t_64_sync_handler+0x44/0xec
el0t_64_sync+0x1a8/0x1ac
Code: 9139c35a 71006f3f 54000568 f8797b55 (f9402ea8)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Oops: Fatal exception
SMP: stopping secondary CPUs
The patch seems to only provide a workaround, but there are no more
effective software solutions to handle the bit flips problem. This path
will change the issue from a system crash to a process exception, thereby
reducing the impact on the entire machine.
Signed-off-by: gao xu <gaoxu2@xxxxxxxxx>
Link: https://lkml.kernel.org/r/e223b0e6ba2f4924984b1917cc717bd5@xxxxxxxxx
Reviewed-by: Barry Song <baohua@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/mm/swapfile.c~mm-fix-possible-null-pointer-dereference-in-__swap_duplicate
+++ a/mm/swapfile.c
@@ -3542,6 +3542,10 @@ static int __swap_duplicate(swp_entry_t
int err, i;
si = swp_swap_info(entry);
+ if (WARN_ON_ONCE(!si)) {
+ pr_err("%s%08lx\n", Bad_file, entry.val);
+ return -EINVAL;
+ }
offset = swp_offset(entry);
VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
_
Patches currently in -mm which might be from gaoxu2@xxxxxxxxx are
mm-fix-possible-null-pointer-dereference-in-__swap_duplicate.patch
