From: Liu Shixin liushixin2@huawei.com
hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6ADCF CVE: NA
--------------------------------
syzbot is reporting GFP_KERNEL allocation with oom_lock held when reporting memcg OOM [1]. If this allocation triggers the global OOM situation then the system can livelock because the GFP_KERNEL allocation with oom_lock held cannot trigger the global OOM killer because __alloc_pages_may_oom() fails to hold oom_lock.
The problem mentioned above has been fixed by patch[2]. The is the same problem in memcg_memfs_info feature too. Refer to the patch[2], fix it by removing the allocation from mem_cgroup_print_memfs_info() completely, and pass static buffer when calling from memcg OOM path.
Link: https://syzkaller.appspot.com/bug?extid=2d2aeadc6ce1e1f11d45 [1] Link: https://lkml.kernel.org/r/86afb39f-8c65-bec2-6cfc-c5e3cd600c0b@I-love.SAKURA... [2] Fixes: 6b1d4d3a3713 ("mm/memcg_memfs_info: show files that having pages charged in mem_cgroup") Signed-off-by: Liu Shixin liushixin2@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Reviewed-by: Cai Xinchen caixinchen1@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- include/linux/memcg_memfs_info.h | 4 +++- mm/memcg_memfs_info.c | 20 ++++++++++---------- mm/memcontrol.c | 3 ++- 3 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/include/linux/memcg_memfs_info.h b/include/linux/memcg_memfs_info.h index 658a91e22bd7..b5e3709baa9e 100644 --- a/include/linux/memcg_memfs_info.h +++ b/include/linux/memcg_memfs_info.h @@ -6,11 +6,13 @@ #include <linux/seq_file.h>
#ifdef CONFIG_MEMCG_MEMFS_INFO -void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, struct seq_file *m); +void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, char *pathbuf, + struct seq_file *m); int mem_cgroup_memfs_files_show(struct seq_file *m, void *v); void mem_cgroup_memfs_info_init(void); #else static inline void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, + char *pathbuf, struct seq_file *m) { } diff --git a/mm/memcg_memfs_info.c b/mm/memcg_memfs_info.c index f404367ad08c..db7b0aee8053 100644 --- a/mm/memcg_memfs_info.c +++ b/mm/memcg_memfs_info.c @@ -157,7 +157,8 @@ static void memfs_show_files_in_mem_cgroup(struct super_block *sb, void *data) mntput(pfc->vfsmnt); }
-void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, struct seq_file *m) +void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, char *pathbuf, + struct seq_file *m) { struct print_files_control pfc = { .memcg = memcg, @@ -165,17 +166,11 @@ void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, struct seq_file *m) .max_print_files = memfs_max_print_files, .size_threshold = memfs_size_threshold, }; - char *pathbuf; int i;
if (!memfs_enable || !memcg) return;
- pathbuf = kmalloc(PATH_MAX, GFP_KERNEL); - if (!pathbuf) { - SEQ_printf(m, "Show memfs failed due to OOM\n"); - return; - } pfc.pathbuf = pathbuf; pfc.pathbuf_size = PATH_MAX;
@@ -192,15 +187,20 @@ void mem_cgroup_print_memfs_info(struct mem_cgroup *memcg, struct seq_file *m) SEQ_printf(m, "total files: %lu, total memory-size: %lukB\n", pfc.total_print_files, pfc.total_files_size >> 10); } - - kfree(pfc.pathbuf); }
int mem_cgroup_memfs_files_show(struct seq_file *m, void *v) { struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m)); + char *pathbuf;
- mem_cgroup_print_memfs_info(memcg, m); + pathbuf = kmalloc(PATH_MAX, GFP_KERNEL); + if (!pathbuf) { + SEQ_printf(m, "Show memfs abort: failed to allocate memory\n"); + return 0; + } + mem_cgroup_print_memfs_info(memcg, pathbuf, m); + kfree(pathbuf); return 0; }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 6344fe257af6..635cb8b65b86 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1611,6 +1611,7 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) { /* Use static buffer, for the caller is holding oom_lock. */ static char buf[PAGE_SIZE]; + static char pathbuf[PATH_MAX];
lockdep_assert_held(&oom_lock);
@@ -1636,7 +1637,7 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) memory_stat_format(memcg, buf, sizeof(buf)); pr_info("%s", buf);
- mem_cgroup_print_memfs_info(memcg, NULL); + mem_cgroup_print_memfs_info(memcg, pathbuf, NULL); }
/*