On Wed, 17 Dec 2025, duziming wrote: > > 在 2025/12/16 18:43, Ilpo Järvinen 写道: > > On Tue, 16 Dec 2025, Ziming Du wrote: > > > > > From: Yongqiang Liu > > > > > > Unaligned access is harmful for non-x86 archs such as arm64. When we > > > use pwrite or pread to access the I/O port resources with unaligned > > > offset, system will crash as follows: > > > > > > Unable to handle kernel paging request at virtual address fffffbfffe8010c1 > > > Internal error: Oops: 0000000096000061 [#1] SMP > > > Modules linked in: > > > CPU: 1 PID: 44230 Comm: syz.1.10955 Not tainted 6.6.0+ #1 > > > Hardware name: linux,dummy-virt (DT) > > > pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > > > pc : __raw_writew arch/arm64/include/asm/io.h:33 [inline] > > > pc : _outw include/asm-generic/io.h:594 [inline] > > > pc : logic_outw+0x54/0x218 lib/logic_pio.c:305 > > > lr : _outw include/asm-generic/io.h:593 [inline] > > > lr : logic_outw+0x40/0x218 lib/logic_pio.c:305 > > > sp : ffff800083097a30 > > > x29: ffff800083097a30 x28: ffffba71ba86e130 x27: 1ffff00010612f93 > > > x26: ffff3bae63b3a420 x25: ffffba71bbf585d0 x24: 0000000000005ac1 > > > x23: 00000000000010c1 x22: ffff3baf0deb6488 x21: 0000000000000002 > > > x20: 00000000000010c1 x19: 0000000000ffbffe x18: 0000000000000000 > > > x17: 0000000000000000 x16: ffffba71b9f44b48 x15: 00000000200002c0 > > > x14: 0000000000000000 x13: 0000000000000000 x12: ffff6775ca80451f > > > x11: 1fffe775ca80451e x10: ffff6775ca80451e x9 : ffffba71bb78cf2c > > > x8 : 0000988a357fbae2 x7 : ffff3bae540228f7 x6 : 0000000000000001 > > > x5 : 1fffe775e2b43c78 x4 : dfff800000000000 x3 : ffffba71b9a00000 > > > x2 : ffff80008d22a000 x1 : ffffc58ec6600000 x0 : fffffbfffe8010c1 > > > Call trace: > > > _outw include/asm-generic/io.h:594 [inline] > > > logic_outw+0x54/0x218 lib/logic_pio.c:305 > > > pci_resource_io drivers/pci/pci-sysfs.c:1157 [inline] > > > pci_write_resource_io drivers/pci/pci-sysfs.c:1191 [inline] > > > pci_write_resource_io+0x208/0x260 drivers/pci/pci-sysfs.c:1181 > > > sysfs_kf_bin_write+0x188/0x210 fs/sysfs/file.c:158 > > > kernfs_fop_write_iter+0x2e8/0x4b0 fs/kernfs/file.c:338 > > > call_write_iter include/linux/fs.h:2085 [inline] > > > new_sync_write fs/read_write.c:493 [inline] > > > vfs_write+0x7bc/0xac8 fs/read_write.c:586 > > > ksys_write+0x12c/0x270 fs/read_write.c:639 > > > __do_sys_write fs/read_write.c:651 [inline] > > > __se_sys_write fs/read_write.c:648 [inline] > > > __arm64_sys_write+0x78/0xb8 fs/read_write.c:648 > > > __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline] > > > invoke_syscall+0x8c/0x2e0 arch/arm64/kernel/syscall.c:51 > > > el0_svc_common.constprop.0+0x200/0x2a8 arch/arm64/kernel/syscall.c:134 > > > do_el0_svc+0x4c/0x70 arch/arm64/kernel/syscall.c:176 > > > el0_svc+0x44/0x1d8 arch/arm64/kernel/entry-common.c:806 > > > el0t_64_sync_handler+0x100/0x130 arch/arm64/kernel/entry-common.c:844 > > > el0t_64_sync+0x3c8/0x3d0 arch/arm64/kernel/entry.S:757 > > > > > > Powerpc seems affected as well, so prohibit the unaligned access > > > on non-x86 archs. > > > > > > Fixes: 8633328be242 ("PCI: Allow read/write access to sysfs I/O port > > > resources") > > > Signed-off-by: Yongqiang Liu > > > Signed-off-by: Ziming Du > > > --- > > > drivers/pci/pci-sysfs.c | 12 ++++++++++++ > > > 1 file changed, 12 insertions(+) > > > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > > > index 7e697b82c5e1..6fa3c9d0e97e 100644 > > > --- a/drivers/pci/pci-sysfs.c > > > +++ b/drivers/pci/pci-sysfs.c > > > @@ -1141,6 +1141,13 @@ static int pci_mmap_resource_wc(struct file *filp, > > > struct kobject *kobj, > > > return pci_mmap_resource(kobj, attr, vma, 1); > > > } > > > +#if !defined(CONFIG_X86) > > > +static bool is_unaligned(unsigned long port, size_t size) > > > +{ > > > + return port & (size - 1); > > > +} > > > +#endif > > > + > > > static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj, > > > const struct bin_attribute *attr, char *buf, > > > loff_t off, size_t count, bool write) > > > @@ -1158,6 +1165,11 @@ static ssize_t pci_resource_io(struct file *filp, > > > struct kobject *kobj, > > > if (port + count - 1 > pci_resource_end(pdev, bar)) > > > return -EINVAL; > > > +#if !defined(CONFIG_X86) > > > + if (is_unaligned(port, count)) > > > + return -EFAULT; > > > +#endif > > > + > > This changes return value from -EINVAL -> -EFAULT for some values of count > > which seems not justified. > > > > To me it's not clear why even x86 should allow unaligned access. This > > interface is very much geared towards natural alignment and sizing of the > > reads (e.g. count = 3 leads to -EINVAL), so it feels somewhat artificial > > to make x86 behave different here from the others. > > Thanks for your review! We verify that when count = 3, the return value will > not be > > -EFAULT; It will only return -EFAULT in cases of unaligned access. Oh, then there's even worse problem in your code as your is_aligned() assumes size is a power of two value. Also, is_aligned() seems to be duplicating IS_ALIGNED() (your naming is very misleading as it's a prefixless name that overlaps with a generic macro with the very same name). > We conduct a POC on QEMU with the ARM architecture as follows: > > #include > #include > #include > > int main() > { >         int fd = open("/sys/bus/pci/devices/0000:00:01.0/resource0", O_RDWR); >         char buf[] = "1233333"; >         if (fd < 0) { >                 printf("open failed\n"); >                 return 1; >         } > >         pwrite(fd, buf, 2, 1); > >         return 0; > } > > On x86, this does not trigger a kernel panic. > > > > switch (count) { > > > case 1: > > > if (write) > > > > -- i.