From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Date: Fri, 12 Jul 2019 03:59:56 +0000 (-0700)
Subject: proc: use down_read_killable mmap_sem for /proc/pid/pagemap
X-Git-Tag: v5.2.5~58
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=69b30136d75be422721d9b223d477c25c8f5f1d5;p=users%2Fdwmw2%2Flinux.git

proc: use down_read_killable mmap_sem for /proc/pid/pagemap

[ Upstream commit ad80b932c57d85fd6377f97f359b025baf179a87 ]

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

Link: http://lkml.kernel.org/r/156007493638.3335.4872164955523928492.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4d9a8e72d91f6..1d9c63cd8a3cd 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1543,7 +1543,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 		/* overflow ? */
 		if (end < start_vaddr || end > end_vaddr)
 			end = end_vaddr;
-		down_read(&mm->mmap_sem);
+		ret = down_read_killable(&mm->mmap_sem);
+		if (ret)
+			goto out_free;
 		ret = walk_page_range(start_vaddr, end, &pagemap_walk);
 		up_read(&mm->mmap_sem);
 		start_vaddr = end;