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From: "Jan H. Schönherr" <jschoenh@amazon.de>
To: Borislav Petkov <bp@alien8.de>
Cc: "Jan H. Schönherr" <jschoenh@amazon.de>,
	"Yazen Ghannam" <yazen.ghannam@amd.com>,
	linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
	"Tony Luck" <tony.luck@intel.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org
Subject: [PATCH v2 3/6] x86/mce: Fix use of uninitialized MCE message string
Date: Fri,  3 Jan 2020 16:07:19 +0100
Message-ID: <20200103150722.20313-4-jschoenh@amazon.de> (raw)
In-Reply-To: <20200103150722.20313-1-jschoenh@amazon.de>

The function mce_severity() is not required to update its msg argument.
In fact, mce_severity_amd() does not, which makes mce_no_way_out()
return uninitialized data, which may be used later for printing.

Assuming that implementations of mce_severity() either always or never
update the msg argument (which is currently the case), it is sufficient
to initialize the temporary variable in mce_no_way_out().

While at it, avoid printing a useless "Unknown".

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
---
Changes v1->v2:
- simplify fix by assuming that mce_severity() either always or never
  updates the msg argument -- as opposed to mce_severity() having the
  freedom to decide on a case by case basis (requested by Boris);
- stop printing "Unknown" (requested by Boris).
---
 arch/x86/kernel/cpu/mce/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 0ccd6cf3402d..1d91ce956772 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -790,7 +790,7 @@ EXPORT_SYMBOL_GPL(machine_check_poll);
 static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp,
 			  struct pt_regs *regs)
 {
-	char *tmp;
+	char *tmp = *msg;
 	int i;
 
 	for (i = 0; i < this_cpu_read(mce_num_banks); i++) {
@@ -1209,8 +1209,8 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
 	struct mca_config *cfg = &mca_cfg;
 	int cpu = smp_processor_id();
-	char *msg = "Unknown";
 	struct mce m, *final;
+	char *msg = NULL;
 	int worst = 0;
 
 	/*
-- 
2.22.0.3.gb49bb57c8208.dirty


  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-03 15:07 [PATCH v2 0/6] x86/mce: Various fixes and cleanups for MCE handling Jan H. Schönherr
2020-01-03 15:07 ` [PATCH v2 1/6] x86/mce: Take action on UCNA/Deferred errors again Jan H. Schönherr
2020-01-10  9:50   ` Borislav Petkov
2020-01-10 18:45     ` Luck, Tony
2020-01-11 13:06       ` Borislav Petkov
2020-01-11 13:17       ` Borislav Petkov
2020-01-03 15:07 ` [PATCH v2 2/6] x86/mce: Make mce=nobootlog work again Jan H. Schönherr
2020-01-03 15:07 ` Jan H. Schönherr [this message]
2020-01-03 15:07 ` [PATCH v2 4/6] x86/mce: Allow a variable number of internal MCE decode notifiers Jan H. Schönherr
2020-01-03 15:07 ` [PATCH v2 5/6] x86/mce: Do not take action on SRAO/Deferred errors on AMD for now Jan H. Schönherr
2020-01-03 15:07 ` [PATCH v2 6/6] x86/mce: Dynamically register default MCE handler Jan H. Schönherr
2020-01-03 19:46   ` Luck, Tony
2020-01-03 21:42   ` Luck, Tony
2020-01-03 22:03   ` Borislav Petkov
2020-01-08  4:24     ` Ghannam, Yazen
2020-01-08 10:03       ` Borislav Petkov
2020-01-09 20:39         ` Ghannam, Yazen
2020-01-09 21:54           ` Luck, Tony
2020-01-09 22:30             ` Jan H. Schönherr
2020-01-04 11:49   ` kbuild test robot

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