Re: [PATCH v2] PCI: Reject negative resource alignment order

[sashiko-bot@kernel.org]

> From: Shao Mingyin <shao.mingyin@zte.com.cn>
> 
> pci_specified_resource_alignment() parses the pci=resource_alignment=
> boot parameter and rejects only orders above 63.  A negative order, such
> as "pci=resource_alignment=-5@...", passes that check and later reaches
> "align = 1ULL << align_order" with a negative shift count, which is
> undefined behavior; on x86 the 64-bit shift count is masked to six bits,
> silently producing a 2^59-byte alignment that mis-aligns (or fails to
> align) the affected IOV resources.
> 
> align_order is a bit order, so parse it with %u.  vsscanf() does not
> accept a sign for %u, so a negative order no longer converts: the
> parameter is reported as invalid and no alignment is applied.  Orders
> above 63 are still rejected and fall back to the page-size alignment.
> 
> Fixes: 6534aac198b5 ("PCI: Bounds-check command-line resource alignment requests")
> Cc: stable@vger.kernel.org
> Signed-off-by: Shao Mingyin <shao.mingyin@zte.com.cn>

Sashiko has reviewed this patch and found no issues.

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