linux-kernel - [PATCH 3.16 095/212] x86/pci-calgary: Fix iommu_free() comparison of unsigned expression >= 0

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Date:   Thu, 01 Jun 2017 16:43:16 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Muli Ben-Yehuda" <mulix@...ix.org>,
        "Nikola Pajkovsky" <npajkovsky@...e.cz>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Jon Mason" <jdmason@...zu.us>, iommu@...ts.linux-foundation.org
Subject: [PATCH 3.16 095/212] x86/pci-calgary: Fix iommu_free() comparison
 of unsigned expression >= 0

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Nikola Pajkovsky <npajkovsky@...e.cz>

commit 68dee8e2f2cacc54d038394e70d22411dee89da2 upstream.

commit 8fd524b355da ("x86: Kill bad_dma_address variable") has killed
bad_dma_address variable and used instead of macro DMA_ERROR_CODE
which is always zero. Since dma_addr is unsigned, the statement

   dma_addr >= DMA_ERROR_CODE

is always true, and not needed.

arch/x86/kernel/pci-calgary_64.c: In function ‘iommu_free’:
arch/x86/kernel/pci-calgary_64.c:299:2: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
  if (unlikely((dma_addr >= DMA_ERROR_CODE) && (dma_addr < badend))) {

Fixes: 8fd524b355da ("x86: Kill bad_dma_address variable")
Signed-off-by: Nikola Pajkovsky <npajkovsky@...e.cz>
Cc: iommu@...ts.linux-foundation.org
Cc: Jon Mason <jdmason@...zu.us>
Cc: Muli Ben-Yehuda <mulix@...ix.org>
Link: http://lkml.kernel.org/r/7612c0f9dd7c1290407dbf8e809def922006920b.1479161177.git.npajkovsky@suse.cz
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kernel/pci-calgary_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -296,7 +296,7 @@ static void iommu_free(struct iommu_tabl
 
 	/* were we called with bad_dma_address? */
 	badend = DMA_ERROR_CODE + (EMERGENCY_PAGES * PAGE_SIZE);
-	if (unlikely((dma_addr >= DMA_ERROR_CODE) && (dma_addr < badend))) {
+	if (unlikely(dma_addr < badend)) {
 		WARN(1, KERN_ERR "Calgary: driver tried unmapping bad DMA "
 		       "address 0x%Lx\n", dma_addr);
 		return;