From: "Theo de Raadt" <deraadt@openbsd.org>
Subject: Re: infinite loop in pcidump
To: Miod Vallat <miod@online.fr>
Cc: tech@openbsd.org
Date: Sat, 29 Aug 2026 20:50:32 -0600

Looks obvious to me.

Miod Vallat <miod@online.fr> wrote:

> I have a PCIe device here, with the whole PCIe configuration space
> read returning all bits set to one (i.e. 0xffffffff).
> 
> When running pcidump -v on this device, I get this:
> 
> 	[...]
> 	0x0100: Enhanced Capability 0xffff: Unknown
> 	0x0ffc: Enhanced Capability 0xffff: Unknown
> 	0x0ffc: Enhanced Capability 0xffff: Unknown
> 	0x0ffc: Enhanced Capability 0xffff: Unknown
> 	0x0ffc: Enhanced Capability 0xffff: Unknown
> 	[ ad nauseam ]
> 
> The following diff tries to recognize this and break from the loop.
> 
> Index: pcidump.c
> ===================================================================
> RCS file: /OpenBSD/src/usr.sbin/pcidump/pcidump.c,v
> diff -u -p -r1.73 pcidump.c
> --- pcidump.c	25 Dec 2025 10:59:26 -0000	1.73
> +++ pcidump.c	29 Aug 2026 05:12:14 -0000
> @@ -675,6 +675,9 @@ dump_pcie_enhanced_caplist(int bus, int 
>  		if (pci_read(bus, dev, func, ptr, &reg) != 0)
>  			return;
>  
> +		if (reg == 0xffffffffU)
> +			return;
> +
>  		if (PCI_PCIE_ECAP_ID(reg) == 0xffff &&
>  		    PCI_PCIE_ECAP_NEXT(reg) == PCI_PCIE_ECAP_LAST)
>  			return;
>