linux-kernel - Re: [GIT PULL] vfs mount

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Message-ID: <20250403182455.GI84568@unreal>
Date: Thu, 3 Apr 2025 21:24:55 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Christian Brauner <brauner@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	pr-tracker-bot@...nel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] vfs mount

On Thu, Apr 03, 2025 at 05:15:38PM +0200, Christian Brauner wrote:
> On Thu, Apr 03, 2025 at 10:29:37AM +0200, Christian Brauner wrote:
> > On Tue, Apr 01, 2025 at 08:07:15PM +0300, Leon Romanovsky wrote:
> > > On Mon, Mar 24, 2025 at 09:00:59PM +0000, pr-tracker-bot@...nel.org wrote:
> > > > The pull request you sent on Sat, 22 Mar 2025 11:13:18 +0100:
> > > > 
> > > > > git@...olite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-6.15-rc1.mount
> > > > 
> > > > has been merged into torvalds/linux.git:
> > > > https://git.kernel.org/torvalds/c/fd101da676362aaa051b4f5d8a941bd308603041
> > > 
> > > I didn't bisect, but this PR looks like the most relevant candidate.
> > > The latest Linus's master generates the following slab-use-after-free:
> > 
> > Sorry, did just see this today. I'll take a look now.
> 
> So in light of "Liberation Day" and the bug that caused this splat it's
> time to quote Max Liebermann:
> 
> "Ich kann nicht so viel fressen, wie ich kotzen möchte."

> From 8822177b7a8a7315446b4227c7eb7a36916a6d6d Mon Sep 17 00:00:00 2001
> From: Christian Brauner <brauner@...nel.org>
> Date: Thu, 3 Apr 2025 16:43:50 +0200
> Subject: [PATCH] fs: actually hold the namespace semaphore
> 
> Don't use a scoped guard use a regular guard to make sure that the
> namespace semaphore is held across the whole function.
> 
> Signed-off-by: Christian Brauner <brauner@...nel.org>
> ---
>  fs/namespace.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 16292ff760c9..348008b9683b 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2478,7 +2478,8 @@ struct vfsmount *clone_private_mount(const struct path *path)
>  	struct mount *old_mnt = real_mount(path->mnt);
>  	struct mount *new_mnt;
>  
> -	scoped_guard(rwsem_read, &namespace_sem)
> +	guard(rwsem_read, &namespace_sem);

I'm looking at Linus's master commit a2cc6ff5ec8f ("Merge tag
'firewire-updates-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394")
and guard is declared as macro which gets only one argument: include/linux/cleanup.h
  318 #define guard(_name) \
  319         CLASS(_name, __UNIQUE_ID(guard))



20:52:24  fs/namespace.c: In function 'clone_private_mount':
20:52:24  fs/namespace.c:2481:41: error: macro "guard" passed 2 arguments, but takes just 1
20:52:24   2481 |         guard(rwsem_read, &namespace_sem);
20:52:24        |                                         ^
20:52:24  In file included from ./include/linux/preempt.h:11,
20:52:24                   from ./include/linux/spinlock.h:56,
20:52:24                   from ./include/linux/wait.h:9,
20:52:24                   from ./include/linux/wait_bit.h:8,
20:52:24                   from ./include/linux/fs.h:7,
20:52:24                   from ./include/uapi/linux/aio_abi.h:31,
20:52:24                   from ./include/linux/syscalls.h:83,
20:52:24                   from fs/namespace.c:11:
20:52:24  ./include/linux/cleanup.h:318:9: note: macro "guard" defined here
20:52:24    318 | #define guard(_name) \
20:52:24        |         ^~~~~
20:52:24  fs/namespace.c:2481:9: error: 'guard' undeclared (first use in this function)
20:52:24   2481 |         guard(rwsem_read, &namespace_sem);
20:52:24        |         ^~~~~
20:52:24  fs/namespace.c:2481:9: note: each undeclared identifier is reported only once for each function it appears in

Do I need to apply extra patch?

Thanks