pstore/ram: Fix undefined usage of rounddown_pow_of_two(0)

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>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 2b6ebbca3521..8741cea6253c 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -376,10 +376,14 @@ 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;