From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA43E3A641D for ; Wed, 15 Jul 2026 14:48:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784126933; cv=none; b=Njja3N9f+LTqXisK+haWDPCvaRdD16Daovx8LS3Swej6eaBubtN3XT1pB7yZ78Pjt7EytQ9PeiiE+pWPO0N0/ecLVghsD+C+zJow3muOGFL0aoKy53l0wBgGucGlZmB45bzm5w6YPJ51kT8Vy0rDvM888asi5pdiBCrTZ8YVbVM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784126933; c=relaxed/simple; bh=VyBUN+/HNGAbAbgimpnUWxtGkIeH7TjXwdnfTKuUX3k=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=Jz8qwQv5J6GCdLEb91n6os27OU5fviVfLrvkbmqmNcl7Z5bIyPJz+6upoBUl6mF9b0Hh1xZsgXNRLE0+ATRFkThS9OvIVVgALWMd3Cm5/tYfQRLfq5MwRkg5tpBYXQA/WHEVys5EWEJoh52ab1e9ErcXXAbv+AdlA21dOAACo+g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2nhpAp2n; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2nhpAp2n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FFE81F000E9; Wed, 15 Jul 2026 14:48:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784126931; bh=CMiWOnlOeLqQ+Hqpb3FVO86YnwXg4Ay3IuhChKDofG4=; h=Subject:To:Cc:From:Date; b=2nhpAp2n89nVnNu/Q20T0bB/T78f5Mxsdin1zIbVDi0jJSUuZU/pm4DWmw9PFcmMk 2gG3W46ity0NIRLQb97f5ZmWtjSpFJ2PkonD0idoUxTh3+C5axAPan93YLGtsCniKz 2cBm1xyalphy5QbjM/P1prEbJ0vnmta9bbEg72yo= Subject: FAILED: patch "[PATCH] mm: do file ownership checks with the proper mount idmap" failed to apply to 5.15-stable tree To: pfalcato@suse.de,akpm@linux-foundation.org,brauner@kernel.org,david@kernel.org,jack@suse.cz,jannh@google.com,liam@infradead.org,stable@vger.kernel.org,vbabka@kernel.org,viro@zeniv.linux.org.uk,willy@infradead.org Cc: From: Date: Wed, 15 Jul 2026 16:48:37 +0200 Message-ID: <2026071536-chirpy-unmindful-fd3a@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-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 . 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-5.15.y git checkout FETCH_HEAD git cherry-pick -x e187bc02f8fa4226d62814592cf064ee4557c470 # git commit -s git send-email --to '' --in-reply-to '2026071536-chirpy-unmindful-fd3a@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From e187bc02f8fa4226d62814592cf064ee4557c470 Mon Sep 17 00:00:00 2001 From: Pedro Falcato Date: Thu, 25 Jun 2026 16:38:53 +0100 Subject: [PATCH] mm: do file ownership checks with the proper mount idmap Ever since idmapped mounts were introduced, inode ownership checks (for side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done against the nop_mnt_idmap, which completely ignores the file's mount's idmap. This results in odd edgecases like: 1) mount/bind-mount with an idmap userA:userB:1 2) userB runs an owner_or_capable() check on file that is owned by userA on-disk/in-memory, but owned by userB after idmap translation 3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied In the case of mincore/madvise MADV_PAGEOUT, this is usually benign, because file_permission(file, MAY_WRITE) will probably succeed, as it uses the proper idmap internally, but it does not need to be the case on e.g a 0444 file where even the owner itself doesn't have permissions to write to it. Since this is clearly not trivial to get right, introduce a file_owner_or_capable() that can carry the correct semantics, and switch the various users in mm to it. The issue was found by manual code inspection & an off-list discussion with Jan Kara. Link: https://lore.kernel.org/20260625153853.913949-1-pfalcato@suse.de Fixes: 9caccd41541a ("fs: introduce MOUNT_ATTR_IDMAP") Signed-off-by: Pedro Falcato Reviewed-by: Jan Kara Reviewed-by: Christian Brauner (Amutable) Acked-by: David Hildenbrand (Arm) Cc: Al Viro Cc: Jann Horn Cc: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton diff --git a/include/linux/fs.h b/include/linux/fs.h index d10897b3a1e3..50ce731a2b78 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2444,6 +2444,11 @@ static inline struct mnt_idmap *file_mnt_idmap(const struct file *file) return mnt_idmap(file->f_path.mnt); } +static inline bool file_owner_or_capable(const struct file *file) +{ + return inode_owner_or_capable(file_mnt_idmap(file), file_inode(file)); +} + /** * is_idmapped_mnt - check whether a mount is mapped * @mnt: the mount to check diff --git a/mm/filemap.c b/mm/filemap.c index 5af62e6abca5..58eb9d240643 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -4704,7 +4704,7 @@ static inline bool can_do_cachestat(struct file *f) { if (f->f_mode & FMODE_WRITE) return true; - if (inode_owner_or_capable(file_mnt_idmap(f), file_inode(f))) + if (file_owner_or_capable(f)) return true; return file_permission(f, MAY_WRITE) == 0; } diff --git a/mm/madvise.c b/mm/madvise.c index cd9bb077072c..77552b03d318 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -336,8 +336,7 @@ static inline bool can_do_file_pageout(struct vm_area_struct *vma) * otherwise we'd be including shared non-exclusive mappings, which * opens a side channel. */ - return inode_owner_or_capable(&nop_mnt_idmap, - file_inode(vma->vm_file)) || + return file_owner_or_capable(vma->vm_file) || file_permission(vma->vm_file, MAY_WRITE) == 0; } diff --git a/mm/mincore.c b/mm/mincore.c index 296f2e3922b5..c8757c5085bf 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -227,8 +227,7 @@ static inline bool can_do_mincore(struct vm_area_struct *vma) * for writing; otherwise we'd be including shared non-exclusive * mappings, which opens a side channel. */ - return inode_owner_or_capable(&nop_mnt_idmap, - file_inode(vma->vm_file)) || + return file_owner_or_capable(vma->vm_file) || file_permission(vma->vm_file, MAY_WRITE) == 0; }