From: "J . Bruce Fields" <bfields@fieldses.org>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
linux-fsdevel@vger.kernel.org,
Lennart Poettering <mzxreary@0pointer.de>
Subject: Re: [PATCH 09/12] statx: add mount_root
Date: Tue, 5 May 2020 10:24:52 -0400 [thread overview]
Message-ID: <20200505142452.GB27314@fieldses.org> (raw)
In-Reply-To: <20200505095915.11275-10-mszeredi@redhat.com>
On Tue, May 05, 2020 at 11:59:12AM +0200, Miklos Szeredi wrote:
> Determining whether a path or file descriptor refers to a mountpoint (or
> more precisely a mount root) is not trivial using current tools.
>
> Add a flag to statx that indicates whether the path or fd refers to the
> root of a mount or not.
A brief summary of the previous discussion might be useful here.
(Comparing st_dev is unreliable for bind mounts; openat2() with
RESOLVE_NO_XDEV works for some use cases but triggers other code
(like security checks and autofs) that are undesirable in other cases:
https://lore.kernel.org/lkml/1450012.1585579399@warthog.procyon.org.uk/T/#ma4516eed1c7507b83343321e3ebd13bba972301c
)
Looks good to me, though.--b.
>
> Reported-by: Lennart Poettering <mzxreary@0pointer.de>
> Reported-by: J. Bruce Fields <bfields@fieldses.org>
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> ---
> fs/stat.c | 3 +++
> include/uapi/linux/stat.h | 1 +
> 2 files changed, 4 insertions(+)
>
> diff --git a/fs/stat.c b/fs/stat.c
> index 3d88c99f7743..b9faa6cafafe 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -202,6 +202,9 @@ int vfs_statx(int dfd, const char __user *filename, int flags,
> error = vfs_getattr(&path, stat, request_mask, flags);
> stat->mnt_id = real_mount(path.mnt)->mnt_id;
> stat->result_mask |= STATX_MNT_ID;
> + if (path.mnt->mnt_root == path.dentry)
> + stat->attributes |= STATX_ATTR_MOUNT_ROOT;
> + stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
> path_put(&path);
> if (retry_estale(error, lookup_flags)) {
> lookup_flags |= LOOKUP_REVAL;
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index d81456247f10..6df9348bb277 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -181,6 +181,7 @@ struct statx {
> #define STATX_ATTR_NODUMP 0x00000040 /* [I] File is not to be dumped */
> #define STATX_ATTR_ENCRYPTED 0x00000800 /* [I] File requires key to decrypt in fs */
> #define STATX_ATTR_AUTOMOUNT 0x00001000 /* Dir: Automount trigger */
> +#define STATX_ATTR_MOUNT_ROOT 0x00002000 /* Root of a mount */
> #define STATX_ATTR_VERITY 0x00100000 /* [I] Verity protected file */
>
>
> --
> 2.21.1
next prev parent reply other threads:[~2020-05-05 14:24 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 9:59 [PATCH 00/12] vfs patch queue Miklos Szeredi
2020-05-05 9:59 ` [PATCH 01/12] vfs: allow unprivileged whiteout creation Miklos Szeredi
2020-05-13 19:12 ` Al Viro
2020-05-05 9:59 ` [PATCH 02/12] aio: fix async fsync creds Miklos Szeredi
2020-05-13 10:01 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 03/12] proc/mounts: add cursor Miklos Szeredi
2020-05-13 19:33 ` Al Viro
2020-05-05 9:59 ` [PATCH 04/12] utimensat: AT_EMPTY_PATH support Miklos Szeredi
2020-05-13 10:02 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 05/12] f*xattr: allow O_PATH descriptors Miklos Szeredi
2020-05-13 10:04 ` Christoph Hellwig
2020-05-14 8:02 ` Miklos Szeredi
2020-05-14 13:01 ` Miklos Szeredi
2020-05-05 9:59 ` [PATCH 06/12] uapi: deprecate STATX_ALL Miklos Szeredi
2020-05-13 10:04 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 07/12] statx: don't clear STATX_ATIME on SB_RDONLY Miklos Szeredi
2020-05-13 10:04 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 08/12] statx: add mount ID Miklos Szeredi
2020-05-13 10:05 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 09/12] statx: add mount_root Miklos Szeredi
2020-05-05 14:24 ` J . Bruce Fields [this message]
2020-05-13 10:05 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 10/12] vfs: don't parse forbidden flags Miklos Szeredi
2020-05-13 10:06 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 11/12] vfs: don't parse "posixacl" option Miklos Szeredi
2020-05-13 10:07 ` Christoph Hellwig
2020-05-05 9:59 ` [PATCH 12/12] vfs: don't parse "silent" option Miklos Szeredi
2020-05-13 10:07 ` Christoph Hellwig
2020-05-13 7:45 ` [13/12 PATCH] vfs: add faccessat2 syscall Miklos Szeredi
2020-05-13 10:09 ` Christoph Hellwig
2020-05-13 7:47 ` [PATCH 00/12] vfs patch queue Miklos Szeredi
2020-05-13 19:48 ` Al Viro
2020-05-14 11:46 ` Miklos Szeredi
2020-05-14 14:55 ` Miklos Szeredi
2020-05-14 15:10 ` Al Viro
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