Date: Tue, 21 May 2024 21:31:54 +0200
From: Michal Hocko <mhocko@...e.com>
To: cve@...nel.org, linux-kernel@...r.kernel.org
Cc: linux-cve-announce@...r.kernel.org, Lee Jones <lee@...nel.org>
Subject: Re: CVE-2024-26650: platform/x86: p2sb: Allow p2sb_bar() calls
 during PCI device probe

This patch has been reverted in upstream by 03c6284df179 ("Revert
"drm/amd/amdgpu: Fix potential ioremap() memory leaks in
amdgpu_device_init()"") and based on the changelog the CVE should be
rejected.

On Tue 26-03-24 17:50:16, Lee Jones wrote:
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe
> 
> p2sb_bar() unhides P2SB device to get resources from the device. It
> guards the operation by locking pci_rescan_remove_lock so that parallel
> rescans do not find the P2SB device. However, this lock causes deadlock
> when PCI bus rescan is triggered by /sys/bus/pci/rescan. The rescan
> locks pci_rescan_remove_lock and probes PCI devices. When PCI devices
> call p2sb_bar() during probe, it locks pci_rescan_remove_lock again.
> Hence the deadlock.
> 
> To avoid the deadlock, do not lock pci_rescan_remove_lock in p2sb_bar().
> Instead, do the lock at fs_initcall. Introduce p2sb_cache_resources()
> for fs_initcall which gets and caches the P2SB resources. At p2sb_bar(),
> refer the cache and return to the caller.
> 
> Before operating the device at P2SB DEVFN for resource cache, check
> that its device class is PCI_CLASS_MEMORY_OTHER 0x0580 that PCH
> specifications define. This avoids unexpected operation to other devices
> at the same DEVFN.
> 
> Tested-by Klara Modin <klarasmodin@...il.com>
> 
> The Linux kernel CVE team has assigned CVE-2024-26650 to this issue.
> 
> 
> Affected and fixed versions
> ===========================
> 
> 	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.1.76 with commit 2841631a0365
> 	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.6.15 with commit 847e1eb30e26
> 	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.7.3 with commit d281ac9a987c
> 	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.8 with commit 5913320eb0b3
> 
> Please see https://www.kernel.org for a full list of currently supported
> kernel versions by the kernel community.
> 
> Unaffected versions might change over time as fixes are backported to
> older supported kernel versions.  The official CVE entry at
> 	https://cve.org/CVERecord/?id=CVE-2024-26650
> will be updated if fixes are backported, please check that for the most
> up to date information about this issue.
> 
> 
> Affected files
> ==============
> 
> The file(s) affected by this issue are:
> 	drivers/platform/x86/p2sb.c
> 
> 
> Mitigation
> ==========
> 
> The Linux kernel CVE team recommends that you update to the latest
> stable kernel version for this, and many other bugfixes.  Individual
> changes are never tested alone, but rather are part of a larger kernel
> release.  Cherry-picking individual commits is not recommended or
> supported by the Linux kernel community at all.  If however, updating to
> the latest release is impossible, the individual changes to resolve this
> issue can be found at these commits:
> 	https://git.kernel.org/stable/c/2841631a03652f32b595c563695d0461072e0de4
> 	https://git.kernel.org/stable/c/847e1eb30e269a094da046c08273abe3f3361cf2
> 	https://git.kernel.org/stable/c/d281ac9a987c553d93211b90fd4fe97d8eca32cd
> 	https://git.kernel.org/stable/c/5913320eb0b3ec88158cfcb0fa5e996bf4ef681b

-- 
Michal Hocko
SUSE Labs

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