linux-kernel - [PATCH] mm/mempolicy: fix lock contention on mems

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220809104927.44366-1-wuyun.abel@bytedance.com>
Date:   Tue,  9 Aug 2022 18:49:27 +0800
From:   Abel Wu <wuyun.abel@...edance.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Muchun Song <songmuchun@...edance.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Abel Wu <wuyun.abel@...edance.com>
Subject: [PATCH] mm/mempolicy: fix lock contention on mems_allowed

The mems_allowed field can be modified by other tasks, so it
isn't safe to access it with alloc_lock unlocked even in the
current process context.

Fixes: 78b132e9bae9 ("mm/mempolicy: remove or narrow the lock on current")
Signed-off-by: Abel Wu <wuyun.abel@...edance.com>
---
 mm/mempolicy.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d39b01fd52fe..ae422e44affb 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -855,12 +855,14 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags,
 		goto out;
 	}
 
+	task_lock(current);
 	ret = mpol_set_nodemask(new, nodes, scratch);
 	if (ret) {
+		task_unlock(current);
 		mpol_put(new);
 		goto out;
 	}
-	task_lock(current);
+
 	old = current->mempolicy;
 	current->mempolicy = new;
 	if (new && new->mode == MPOL_INTERLEAVE)
@@ -1295,7 +1297,9 @@ static long do_mbind(unsigned long start, unsigned long len,
 		NODEMASK_SCRATCH(scratch);
 		if (scratch) {
 			mmap_write_lock(mm);
+			task_lock(current);
 			err = mpol_set_nodemask(new, nmask, scratch);
+			task_unlock(current);
 			if (err)
 				mmap_write_unlock(mm);
 		} else
-- 
2.31.1