linux-kernel - [PATCH][next] perf/x86/intel/uncore: Fix integer overflow on 23 bit left shift of a u32

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Date:   Tue,  6 Jul 2021 12:45:53 +0100
From:   Colin King <colin.king@...onical.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-perf-users@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] perf/x86/intel/uncore: Fix integer overflow on 23 bit left shift of a u32

From: Colin Ian King <colin.king@...onical.com>

The u32 variable pci_dword is being masked with 0x1fffffff and then left
shifted 23 places. The shift is a u32 operation,so a value of 0x200 or
more in pci_dword will overflow the u32 and only the bottow 32 bits
are assigned to addr. I don't believe this was the original intent.
Fix this by casting pci_dword to a resource_size_t to ensure no
overflow occurs.

Note that the mask and 12 bit left shift operation does not need this
because the mask SNR_IMC_MMIO_MEM0_MASK and shift is always a 32 bit
value.

Fixes: ee49532b38dd ("perf/x86/intel/uncore: Add IMC uncore support for Snow Ridge")
Addresses-Coverity: ("Unintentional integer overflow")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 arch/x86/events/intel/uncore_snbep.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
index 48419dad3b17..7518143850df 100644
--- a/arch/x86/events/intel/uncore_snbep.c
+++ b/arch/x86/events/intel/uncore_snbep.c
@@ -4827,7 +4827,7 @@ static int snr_uncore_mmio_map(struct intel_uncore_box *box,
 		return -ENODEV;
 
 	pci_read_config_dword(pdev, SNR_IMC_MMIO_BASE_OFFSET, &pci_dword);
-	addr = (pci_dword & SNR_IMC_MMIO_BASE_MASK) << 23;
+	addr = ((resource_size_t)pci_dword & SNR_IMC_MMIO_BASE_MASK) << 23;
 
 	pci_read_config_dword(pdev, mem_offset, &pci_dword);
 	addr |= (pci_dword & SNR_IMC_MMIO_MEM0_MASK) << 12;
-- 
2.31.1