diff mbox series

[v4] mm: Fix possible NULL pointer dereference in __swap_duplicate

Message ID e223b0e6ba2f4924984b1917cc717bd5@honor.com (mailing list archive)
State New
Headers show
Series [v4] mm: Fix possible NULL pointer dereference in __swap_duplicate | expand

Commit Message

gaoxu Feb. 19, 2025, 1:56 a.m. UTC 
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@honor.com>
---
v1 -> v2: 
- Add WARN_ON_ONCE.
- update the commit info.
v2 -> v3: Delete the review tags (This is my issue, and I apologize).
V3 -> v4: Add swap entry logging per Barry Song's suggestion.
---
 mm/swapfile.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Barry Song Feb. 19, 2025, 2:28 a.m. UTC | #1 
On Wed, Feb 19, 2025 at 2:56 PM gaoxu <gaoxu2@honor.com> wrote:
>
> 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@honor.com>

Regardless of whether the above statement is 100% accurate or whether
a bit-flip actually exists, providing this check still seems useful,
at least for
defensive programming.

Reviewed-by: Barry Song <baohua@kernel.org>

> ---
> v1 -> v2:
> - Add WARN_ON_ONCE.
> - update the commit info.
> v2 -> v3: Delete the review tags (This is my issue, and I apologize).
> V3 -> v4: Add swap entry logging per Barry Song's suggestion.
> ---
>  mm/swapfile.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 7448a3876..403df1817 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -3521,6 +3521,10 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
>         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);
> --
> 2.17.1
Andrew Morton Feb. 19, 2025, 4:03 a.m. UTC | #2 
On Wed, 19 Feb 2025 15:28:26 +1300 Barry Song <21cnbao@gmail.com> wrote:

> > 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@honor.com>
> 
> Regardless of whether the above statement is 100% accurate or whether
> a bit-flip actually exists, providing this check still seems useful,
> at least for
> defensive programming.

I'm doubtful as well.

How often has this crash been observed?
gaoxu Feb. 19, 2025, 6:23 a.m. UTC | #3 
> 
> On Wed, 19 Feb 2025 15:28:26 +1300 Barry Song <21cnbao@gmail.com>
> wrote:
> 
> > > 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@honor.com>
> >
> > Regardless of whether the above statement is 100% accurate or whether
> > a bit-flip actually exists, providing this check still seems useful,
> > at least for defensive programming.
> 
> I'm doubtful as well.
> 
> How often has this crash been observed?
The probability of this issue occurring is approximately 1 in 500,000 per week.
diff mbox series

Patch

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7448a3876..403df1817 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3521,6 +3521,10 @@  static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
 	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);