From: Zilin Guan <zilin@seu.edu.cn>
Date: Wed, 5 Nov 2025 02:29:23 +0000 (+0000)
Subject: binfmt_misc: restore write access before closing files opened by open_exec()
X-Git-Tag: v6.18-rc7~32^2~5
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=90f601b497d76f40fa66795c3ecf625b6aced9fd;p=thirdparty%2Flinux.git

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@seu.edu.cn>
Link: https://patch.msgid.link/20251105022923.1813587-1-zilin@seu.edu.cn
Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a839f960cd4a0..a8b1d79e4af07 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -837,8 +837,10 @@ out:
 	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;
 	}