linux-kernel - [PATCH] userfaultfd: avoid the duplicated release for userfaultfd

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Date:   Wed, 15 Jul 2020 00:12:03 +0800
From:   <yanfei.xu@...driver.com>
To:     <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] userfaultfd: avoid the duplicated release for userfaultfd_ctx

From: Yanfei Xu <yanfei.xu@...driver.com>

when get_unused_fd_flags gets failure, userfaultfd_ctx_cachep will
be freed by userfaultfd_fops's release function which is the
userfaultfd_release. So we could return directly after fput().

userfaultfd_release()->userfaultfd_ctx_put(ctx)

Fixes: d08ac70b1e0d (Wire UFFD up to SELinux)
Reported-by: syzbot+75867c44841cb6373570@...kaller.appspotmail.com
Signed-off-by: Yanfei Xu <yanfei.xu@...driver.com>
---
 fs/userfaultfd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 3a4d6ac5a81a..e98317c15530 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -2049,7 +2049,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
 	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
 	if (fd < 0) {
 		fput(file);
-		goto out;
+		return fd;
 	}
 
 	ctx->owner = file_inode(file);
-- 
2.18.2