| Message ID | 20210923020524.13289-1-chenjun102@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3,1/1] mm: Fix the uninitialized use in overcommit_policy_handler | expand |
On Thu, 23 Sep 2021 02:05:24 +0000 Chen Jun <chenjun102@huawei.com> wrote: > 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. > Thanks. I added a cc:stable to this, so the fix will be backported into earlier kernels.
On 2021/9/24 10:23, Andrew Morton wrote: > On Thu, 23 Sep 2021 02:05:24 +0000 Chen Jun <chenjun102@huawei.com> wrote: > >> 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) Hi Andrew， missing ';' here, > Thanks. I added a cc:stable to this, so the fix will be backported > into earlier kernels. ... and the Fixes tag miss a ')' in the end , please help to add them :) Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
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);
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(-)