linux-kernel - [PATCH v2] PCI/AER: Avoid info leak in __print_tlp

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Message-Id: <1424940903-9147-1-git-send-email-linux@rasmusvillemoes.dk>
Date:	Thu, 26 Feb 2015 09:55:03 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Borislav Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] PCI/AER: Avoid info leak in __print_tlp_header

Commit fab4c256a58b ("PCI/AER: Add a TLP header print helper")
introduced the helper function __print_tlp_header, but contrary to the
intention, the behaviour did change: Since we're taking the address of
the parameter t, the first 4 or 8 bytes printed will be the value of
the pointer t itself, and the remaining 12 or 8 bytes will be
who-knows-what (something from the stack).

We want to show the values of the four members of the struct
aer_header_log_regs; that can be done without ugly and error-prone
casts. On little-endian this should produce the same output as
originally intended, and since no-one has complained about getting
garbage output so far, I think big-endian should be ok too.

Fixes: fab4c256a58b ("PCI/AER: Add a TLP header print helper")
Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
v2: Just print ->dwX as-is.

 drivers/pci/pcie/aer/aerdrv_errprint.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/pcie/aer/aerdrv_errprint.c b/drivers/pci/pcie/aer/aerdrv_errprint.c
index c6849d9e86ce..167fe411ce2e 100644
--- a/drivers/pci/pcie/aer/aerdrv_errprint.c
+++ b/drivers/pci/pcie/aer/aerdrv_errprint.c
@@ -132,16 +132,8 @@ static const char *aer_agent_string[] = {
 static void __print_tlp_header(struct pci_dev *dev,
 			       struct aer_header_log_regs *t)
 {
-	unsigned char *tlp = (unsigned char *)&t;
-
-	dev_err(&dev->dev, "  TLP Header:"
-		" %02x%02x%02x%02x %02x%02x%02x%02x"
-		" %02x%02x%02x%02x %02x%02x%02x%02x\n",
-		*(tlp + 3), *(tlp + 2), *(tlp + 1), *tlp,
-		*(tlp + 7), *(tlp + 6), *(tlp + 5), *(tlp + 4),
-		*(tlp + 11), *(tlp + 10), *(tlp + 9),
-		*(tlp + 8), *(tlp + 15), *(tlp + 14),
-		*(tlp + 13), *(tlp + 12));
+	dev_err(&dev->dev, "  TLP Header: %08x %08x %08x %08x\n",
+		t->dw0, t->dw1, t->dw2, t->dw3);
 }
 
 static void __aer_print_error(struct pci_dev *dev,
-- 
2.1.3

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