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Subject[PATCH] sched: fix information leak in sys_sched_getattr()
Date
From: Vegard Nossum <vegard.nossum@oracle.com>

We're copying the on-stack structure to userspace, but forgot to give
the right number of bytes to copy. This allows the calling process to
obtain up to PAGE_SIZE bytes from the stack (and possibly adjacent
kernel memory).

This fix copies only as much as we actually have on the stack
(attr->size defaults to the size of the struct) and leaves the rest of
the userspace-provided buffer untouched.

Found using kmemcheck + trinity.

Fixes: d50dde5a10f30 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI")
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b46131e..ac939c3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3786,7 +3786,7 @@ static int sched_read_attr(struct sched_attr __user *uattr,
attr->size = usize;
}

- ret = copy_to_user(uattr, attr, usize);
+ ret = copy_to_user(uattr, attr, attr->size);
if (ret)
return -EFAULT;

--
1.7.10.4


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