From: Chen Jun <chenjun102@huawei.com>
To: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Cc: <akpm@linux-foundation.org>, <feng.tang@intel.com>,
<mhocko@suse.com>, <rui.xiang@huawei.com>
Subject: [PATCH v3 1/1] mm: Fix the uninitialized use in overcommit_policy_handler
Date: Thu, 23 Sep 2021 02:05:24 +0000 [thread overview]
Message-ID: <20210923020524.13289-1-chenjun102@huawei.com> (raw)
An unexpected value of /proc/sys/vm/overcommit_memory we will get,
after running the following program.
int main()
{
int fd = open("/proc/sys/vm/overcommit_memory", O_RDWR)
write(fd, "1", 1);
write(fd, "2", 1);
close(fd);
}
write(fd, "2", 1) will pass *ppos = 1 to proc_dointvec_minmax.
proc_dointvec_minmax will return 0 without setting new_policy.
t.data = &new_policy;
ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos)
-->do_proc_dointvec
-->__do_proc_dointvec
if (write) {
if (proc_first_pos_non_zero_ignore(ppos, table))
goto out;
sysctl_overcommit_memory = new_policy;
so sysctl_overcommit_memory will be set to an uninitialized value.
Check whether new_policy has been changed by proc_dointvec_minmax.
Fixes: 56f3547bfa4d ("mm: adjust vm_committed_as_batch according to vm overcommit policy"
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Feng Tang <feng.tang@intel.com>
---
v3:
* Correct commit message.
v2:
* Check whether new_policy has been changed by proc_dointvec_minmax.
mm/util.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/util.c b/mm/util.c
index 4ddb6e186dd5..d5be67771850 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -756,7 +756,7 @@ int overcommit_policy_handler(struct ctl_table *table, int write, void *buffer,
size_t *lenp, loff_t *ppos)
{
struct ctl_table t;
- int new_policy;
+ int new_policy = -1;
int ret;
/*
@@ -774,7 +774,7 @@ int overcommit_policy_handler(struct ctl_table *table, int write, void *buffer,
t = *table;
t.data = &new_policy;
ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
- if (ret)
+ if (ret || new_policy == -1)
return ret;
mm_compute_batch(new_policy);
--
2.17.1
next reply other threads:[~2021-09-23 2:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-23 2:05 Chen Jun [this message]
2021-09-24 2:23 ` [PATCH v3 1/1] mm: Fix the uninitialized use in overcommit_policy_handler Andrew Morton
2021-09-24 2:41 ` Kefeng Wang
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