回复: [PATCH v2] mm: Fix possible NULL pointer dereference in __swap_duplicate

[gaoxu <gaoxu2@honor.com>]

> 
> February 14, 2025 at 10:52 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: gaoxu <gaoxu2@honor.com>
> >
> > Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
> 
> 
> I did not review this patch, I only made a suggestion. Please only add Review
> tags when explicitly given.
sorry, I will resend a patch that removes the Review tags.