[Devel] [PATCH VZ10 2/2] libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()

[Vladimir Riabchun]

On 7/27/26 14:22, Pavel Tikhomirov wrote:
> From: John Hubbard <jhubbard at nvidia.com>
> 
> Since commit 1e7ab6f67824 ("anon_inode: rework assertions"),
> path_noexec() warns when an anonymous-inode file is mmap'd from a
> superblock that has not set SB_I_NOEXEC. dma-buf backs its files this
> way and never set the flag, so mmap of any exported buffer trips the
> warning on a CONFIG_DEBUG_VFS=y kernel:
> 
>    WARNING: CPU: 11 PID: 121813 at fs/exec.c:118 path_noexec+0x47/0x50
>     do_mmap+0x2b5/0x680
>     vm_mmap_pgoff+0x129/0x210
>     ksys_mmap_pgoff+0x177/0x240
>     __x64_sys_mmap+0x33/0x70
> 
> init_pseudo() sets up internal SB_NOUSER mounts that are never
> path-reachable. Set both flags here so every pseudo filesystem gets
> them by default instead of each caller setting them.
> 
> SB_I_NODEV is inert for unreachable mounts. SB_I_NOEXEC has one
> visible effect: an executable mapping of a pseudo-fs fd, such as a
> dma-buf, now fails with -EPERM, which is the invariant the assertion
> enforces. No in-tree caller maps these executable.
> 
> Reproduce on CONFIG_DEBUG_VFS=y:
> 
>    make -C tools/testing/selftests/dmabuf-heaps
>    sudo ./tools/testing/selftests/dmabuf-heaps/dmabuf-heap -t system
> 
> Fixes: 1e7ab6f67824 ("anon_inode: rework assertions")
> Suggested-by: Christoph Hellwig <hch at infradead.org>
> Cc: stable at vger.kernel.org
> Signed-off-by: John Hubbard <jhubbard at nvidia.com>
> Link: https://patch.msgid.link/20260604025315.245910-2-jhubbard@nvidia.com
> Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
> 
> (cherry picked from commit 6de2aeffabaafaeda819e60ec8d04f199711e11a)
> Feature: ve: CRIU support
> https://virtuozzo.atlassian.net/browse/VSTOR-139264
> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>

Reviewed-by: Vladimir Riabchun <vladimir.riabchun at virtuozzo.com>

> ---
>   fs/libfs.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/fs/libfs.c b/fs/libfs.c
> index af191a388303c..17a0a4d9bfe8b 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -721,6 +721,7 @@ struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
>   		fc->fs_private = ctx;
>   		fc->ops = &pseudo_fs_context_ops;
>   		fc->sb_flags |= SB_NOUSER;
> +		fc->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
>   		fc->global = true;
>   	}
>   	return ctx;

-- 
Best regards, Riabchun Vladimir
Linux Kernel Developer, Virtuozzo