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Subject[PATCH 02/10] module: fix out-of-range memory access
Date
Impact: subtle memory access bug fix

percpu_modalloc() may access pcpu_size[-1]. The access won't change
the value by itself but it still is read/write access and dangerous.
Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/module.c | 14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index ba22484..d54a63e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -426,12 +426,14 @@ static void *percpu_modalloc(unsigned long size, unsigned long align,
continue;

/* Transfer extra to previous block. */
- if (pcpu_size[i-1] < 0)
- pcpu_size[i-1] -= extra;
- else
- pcpu_size[i-1] += extra;
- pcpu_size[i] -= extra;
- ptr += extra;
+ if (extra) {
+ if (pcpu_size[i-1] < 0)
+ pcpu_size[i-1] -= extra;
+ else
+ pcpu_size[i-1] += extra;
+ pcpu_size[i] -= extra;
+ ptr += extra;
+ }

/* Split block if warranted */
if (pcpu_size[i] - size > sizeof(unsigned long))
--
1.6.0.2


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