FAILED: patch "[PATCH] fscrypt: use the mount idmap for the owner check in" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x cf6c993c0feca7984797e634deba3c80342e199a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026081749-arrest-overfill-06b8@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cf6c993c0feca7984797e634deba3c80342e199a Mon Sep 17 00:00:00 2001
From: Zhan Xusheng <[email protected]>
Date: Sat, 25 Jul 2026 16:00:04 +0800
Subject: [PATCH] fscrypt: use the mount idmap for the owner check in
 fscrypt_ioctl_set_policy()

fscrypt_ioctl_set_policy() calls inode_owner_or_capable() with
&nop_mnt_idmap before allowing an encryption policy to be set, instead
of the idmap of the mount the ioctl was issued on.

fscrypt is used by filesystems that support idmapped mounts (e.g. ext4,
f2fs), so on such a mount this compares the caller's fsuid against the
unmapped on-disk owner rather than the mapped owner: the actual owner
can be wrongly denied with -EACCES and an unrelated caller wrongly
allowed.  Use file_mnt_idmap(filp) instead.

Fixes: 14f3db5542e6 ("ext4: support idmapped mounts")
Cc: [email protected]
Signed-off-by: Zhan Xusheng <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Eric Biggers <[email protected]>

diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index 9915e39362db..c80b24a941ad 100644
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -534,7 +534,7 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 		return -EFAULT;
 	policy.version = version;
 
-	if (!inode_owner_or_capable(&nop_mnt_idmap, inode))
+	if (!inode_owner_or_capable(file_mnt_idmap(filp), inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(filp);