From: Chen Jun chenjun102@huawei.com
maillist inclusion category: bugfix bugzilla: 182215 https://gitee.com/openeuler/kernel/issues/I4DDEL
Reference: https://lore.kernel.org/linux-mm/20210922014122.47219-1-chenjun102@huawei.co...
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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 Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Signed-off-by: Chen Jun chenjun102@huawei.com --- 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);