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Subject[PATCH v2] pstore/ram: fix undefined usage of rounddown_pow_of_two(0)
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From: Maxime Bizon <mbizon@freebox.fr>

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).

CC: stable@vger.kernel.org
Signed-off-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Florian Fainelli <ffainelli@freebox.fr>
---
Changes since v1:
- use !is_power_of_2(size) instead of (!size)

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

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 1a4f6da..bdd840d 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -374,10 +374,14 @@ static int __devinit ramoops_probe(struct platform_device *pdev)
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;
--
1.7.9.5


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