Re: [PATCH] HID: amd_sfh: Validate PCI BAR size before mapping

[Slawomir Stepien <sst@poczta.fm>]

On wrz 11, 2026 21:33, Basavaraj Natikar wrote:
> 
> On 8/27/2026 12:06 PM, syzbot wrote:
> > [You don't often get email from syzbot@kernel.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > 
> > From: Slawomir Stepien <sst@poczta.fm>
> > 
> > The amd_sfh driver maps PCI BAR 2 using pcim_iomap_regions() and
> > subsequently accesses MMIO registers at offsets up to 0x10958 (e.g.,
> > AMD_P2C_MSG3 at 0x1068C). However, the driver never validates that the BAR
> > size is large enough to cover these accesses. If the driver is bound to a
> > device with a smaller BAR 2, this leads to an out-of-bounds memory access
> > and a page fault during the probe function.
> > 
> > For example, a page fault can occur when reading from privdata->mmio +
> > AMD_P2C_MSG3 in mp2_select_ops():
> > 
> >    BUG: unable to handle page fault for address: ffffc9000390368c
> >    PGD 100000067 P4D 100000067 PUD 1012c1067 PMD 105b64067 PTE 0
> >    Oops: Oops: 0000 [#1] SMP KASAN NOPTI
> >    RIP: 0010:readl arch/x86/include/asm/io.h:59 [inline]
> >    RIP: 0010:mp2_select_ops drivers/hid/amd-sfh-hid/amd_sfh_pcie.c:282
> >    [inline]
> >    RIP: 0010:amd_mp2_pci_probe+0x337/0x5f0
> >    drivers/hid/amd-sfh-hid/amd_sfh_pcie.c:487
> >    Call Trace:
> >     <TASK>
> >     local_pci_probe drivers/pci/pci-driver.c:332 [inline]
> >     pci_call_probe drivers/pci/pci-driver.c:394 [inline]
> >     __pci_device_probe drivers/pci/pci-driver.c:455 [inline]
> >     pci_device_probe+0x431/0xc90 drivers/pci/pci-driver.c:489
> > 
> > Fix this by verifying that the length of BAR 2 is at least 128KB before
> > attempting to map it. Since the maximum accessed offset is 0x10958, and PCI
> > BAR sizes are powers of 2, any legitimate hardware will have a BAR size of
> > at least 128KB.
> > 
> > Fixes: 4f567b9f8141 ("SFH: PCIe driver to add support of AMD sensor fusion hub")
> > Assisted-by: Gemini:gemini-3.7-flash Gemini:gemini-3.1-pro-preview syzbot
> > Reported-by: syzbot+4eadd4dfe9e66522bae8@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=4eadd4dfe9e66522bae8
> > Link: https://syzkaller.appspot.com/ai_job?id=3bc1c45c-548f-4ab5-8243-d2c8ec321d6c
> > Signed-off-by: Slawomir Stepien <sst@poczta.fm>
> > 
> > ---
> > diff --git a/drivers/hid/amd-sfh-hid/amd_sfh_common.h b/drivers/hid/amd-sfh-hid/amd_sfh_common.h
> > index 78f830c13..c0c324565 100644
> > --- a/drivers/hid/amd-sfh-hid/amd_sfh_common.h
> > +++ b/drivers/hid/amd-sfh-hid/amd_sfh_common.h
> > @@ -17,6 +17,8 @@
> >   #define PCI_DEVICE_ID_AMD_MP2          0x15E4
> >   #define PCI_DEVICE_ID_AMD_MP2_1_1      0x164A
> > 
> > +#define AMD_SFH_MIN_BAR_SIZE           (128 * 1024)
> 
> Please use SZ_128K instead of the open-coded (128 * 1024), A short comment noting the value
> must cover the highest register offset (0x10958) would also help future readers.
> 
> With that:
> Acked-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>

Sure, will send v2, thanks!

-- 
Slawomir Stepien