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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 6623A8000A X-Stat-Signature: 4mc3wjz8epaat59hqrachesfxns4kwd9 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1739932118-799777 X-HE-Meta: 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 GyjeXpJw WtfmzZ0hOvPYzyWVMO3ze4+KB+7R5whN58KB1/uRv2TikIMoaufEapK1V0hg/UJQ9ayPmiRbqq3tCkIPbWbaJT78VHfBOONQP/snPoN0XESaz8XnEKbqqpn3X/SZYm82bvw65UXXH1nqF19E/xkc1ivWZQUycM9o5c4LrkDyo7zdDKXpg3rHHOJuzsyTUTOYuU70At01BqehSa9UE+ddUql0DtcZ9iIZ72qW8+FdUxGfwFHn+lk2b4RfC6AOMRo7JoLLdIjus9j9gLXTWnTJroHTx5cAlGmlibJFojx7N/n2ePURZ4GmsIH8NA244WOsirVgZtOZwfgqkd3fVvPM0i9y/7dvmE7rhkggV4nyxuvIHGvFVk3/pyd6q3TfaG6Wl5N5xW6oeiTjCWyFmO9AnKSHrRWh8N8/0oPf+R3YkR3fd4kjtTYtZx9r3kwgYFsXiLdsl/kWWWmsp4Z3Dnh9xLo1VyWGzgvYgArmWrdbzSPpOpq0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 19, 2025 at 2:56=E2=80=AFPM gaoxu 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=EF=BC=9A > 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 =3D 0x0000000096000005 > EC =3D 0x25: DABT (current EL), IL =3D 32 bits > SET =3D 0, FnV =3D 0 > EA =3D 0, S1PTW =3D 0 > FSC =3D 0x05: level 1 translation fault > Data abort info: > ISV =3D 0, ISS =3D 0x00000005, ISS2 =3D 0x00000000 > CM =3D 0, WnR =3D 0, TnD =3D 0, TagAccess =3D 0 > GCS =3D 0, Overlay =3D 0, DirtyBit =3D 0, Xs =3D 0 > user pgtable: 4k pages, 39-bit VAs, pgdp=3D00000008a80e5000 > [0000000000000058] pgd=3D0000000000000000, p4d=3D0000000000000000, > pud=3D0000000000000000 > 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 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 > --- > 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, uns= igned char usage, int nr) > int err, i; > > si =3D swp_swap_info(entry); > + if (WARN_ON_ONCE(!si)) { > + pr_err("%s%08lx\n", Bad_file, entry.val); > + return -EINVAL; > + } > > offset =3D swp_offset(entry); > VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER); > -- > 2.17.1