linux-kernel - [ 045/221] pstore/ram: Fix undefined usage of rounddown_pow_of

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Message-Id: <20130115185001.268335036@linuxfoundation.org>
Date:	Tue, 15 Jan 2013 10:49:32 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Maxime Bizon <mbizon@...ebox.fr>,
	Florian Fainelli <ffainelli@...ebox.fr>,
	Kees Cook <keescook@...omium.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>
Subject: [ 045/221] pstore/ram: Fix undefined usage of rounddown_pow_of_two(0)

3.7-stable review patch.  If anyone has any objections, please let me know.

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

From: Maxime Bizon <mbizon@...ebox.fr>

commit b042e47491ba5f487601b5141a3f1d8582304170 upstream.

record_size / console_size / ftrace_size can be 0 (this is how you disable
the feature), but rounddown_pow_of_two(0) is undefined. As suggested by
Kees Cook, use !is_power_of_2() as a condition to call
rounddown_pow_of_two and avoid its undefined behavior on the value 0. This
issue has been present since commit 1894a253 (ramoops: Move to
fs/pstore/ram.c).

Signed-off-by: Maxime Bizon <mbizon@...ebox.fr>
Signed-off-by: Florian Fainelli <ffainelli@...ebox.fr>
Acked-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/pstore/ram.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -374,10 +374,14 @@ static int __devinit ramoops_probe(struc
 		goto fail_out;
 	}
 
-	pdata->mem_size = rounddown_pow_of_two(pdata->mem_size);
-	pdata->record_size = rounddown_pow_of_two(pdata->record_size);
-	pdata->console_size = rounddown_pow_of_two(pdata->console_size);
-	pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
+	if (!is_power_of_2(pdata->mem_size))
+		pdata->mem_size = rounddown_pow_of_two(pdata->mem_size);
+	if (!is_power_of_2(pdata->record_size))
+		pdata->record_size = rounddown_pow_of_two(pdata->record_size);
+	if (!is_power_of_2(pdata->console_size))
+		pdata->console_size = rounddown_pow_of_two(pdata->console_size);
+	if (!is_power_of_2(pdata->ftrace_size))
+		pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
 
 	cxt->dump_read_cnt = 0;
 	cxt->size = pdata->mem_size;


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