From: Christian Brauner <brauner@kernel.org>
Date: Fri, 10 Jul 2026 09:33:02 +0000 (+0200)
Subject: binfmt_misc: restore write access when removing an entry
X-Git-Tag: v7.2-rc6~6^2~4
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=db1856ea9196cf6e015d12199a34c0b9313c7bfa;p=thirdparty%2Flinux.git

binfmt_misc: restore write access when removing an entry

Registering an entry with the MISC_FMT_OPEN_FILE flag opens the
interpreter via open_exec() which denies write access to it for as
long as the entry exists. Removing the entry closes the interpreter
file via filp_close() but never restores write access, leaving the
inode's i_writecount permanently negative. Opening the interpreter
for writing keeps failing with ETXTBSY long after the entry is gone
until the inode is evicted from the inode cache.

Commit 90f601b497d7 ("binfmt_misc: restore write access before
closing files opened by open_exec()") fixed the same imbalance in the
error path of bm_register_write() but the actual removal path has
been leaking the write denial since the introduction of the flag.

Restore write access in put_binfmt_handler() before closing the
interpreter file.

Link: https://patch.msgid.link/20260710-work-binfmt_misc-locking-v3-1-a162f7cb58d6@kernel.org
Fixes: 948b701a607f ("binfmt_misc: add persistent opened binary handler for containers")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 47aeb2b68d3e..adab06d18550 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -162,8 +162,10 @@ static Node *get_binfmt_handler(struct binfmt_misc *misc,
 static void put_binfmt_handler(Node *e)
 {
 	if (refcount_dec_and_test(&e->users)) {
-		if (e->flags & MISC_FMT_OPEN_FILE)
+		if (e->flags & MISC_FMT_OPEN_FILE) {
+			exe_file_allow_write_access(e->interp_file);
 			filp_close(e->interp_file, NULL);
+		}
 		kfree(e);
 	}
 }