linux-kernel - [PATCH] binfmt_misc: restore write access before closing files opened by open

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 for Android: free password hash cracker in your pocket

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

Message-Id: <20251105022923.1813587-1-zilin@seu.edu.cn>
Date: Wed,  5 Nov 2025 02:29:23 +0000
From: Zilin Guan <zilin@....edu.cn>
To: viro@...iv.linux.org.uk
Cc: brauner@...nel.org,
	jack@...e.cz,
	kees@...nel.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	jianhao.xu@....edu.cn,
	Zilin Guan <zilin@....edu.cn>
Subject: [PATCH] binfmt_misc: restore write access before closing files opened by open_exec()

bm_register_write() opens an executable file using open_exec(), which
internally calls do_open_execat() and denies write access on the file to
avoid modification while it is being executed.

However, when an error occurs, bm_register_write() closes the file using
filp_close() directly. This does not restore the write permission, which
may cause subsequent write operations on the same file to fail.

Fix this by calling exe_file_allow_write_access() before filp_close() to
restore the write permission properly.

Fixes: e7850f4d844e ("binfmt_misc: fix possible deadlock in bm_register_write")
Signed-off-by: Zilin Guan <zilin@....edu.cn>
---
 fs/binfmt_misc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a839f960cd4a..a8b1d79e4af0 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -837,8 +837,10 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 	inode_unlock(d_inode(root));

 	if (err) {
-		if (f)
+		if (f) {
+			exe_file_allow_write_access(f);
 			filp_close(f, NULL);
+		}
 		kfree(e);
 		return err;
 	}
-- 
2.34.1