From: Chen Jun chenjun102@huawei.com
commit bcbda81020c3ee77e2c098cadf3e84f99ca3de17 upstream.
We get an unexpected value of /proc/sys/vm/overcommit_memory 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.
Link: https://lkml.kernel.org/r/20210923020524.13289-1-chenjun102@huawei.com 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 Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Cc: Rui Xiang rui.xiang@huawei.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/util.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/util.c +++ b/mm/util.c @@ -768,7 +768,7 @@ int overcommit_policy_handler(struct ctl size_t *lenp, loff_t *ppos) { struct ctl_table t; - int new_policy; + int new_policy = -1; int ret;
/* @@ -786,7 +786,7 @@ int overcommit_policy_handler(struct ctl 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);