diff options
| author | Aleksa Sarai <cyphar@cyphar.com> | 2025-07-08 23:21:51 +1000 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-07-10 09:39:18 +0200 |
| commit | 76fdb7eb4e1c91086ce9c3db6972c2ed48c96afb (patch) | |
| tree | b8db83fb32e4008f3dfb2c2b7fc04c5631ae82f8 /fs/proc/root.c | |
| parent | cd267cdef5fe98006a6b989c5cda035032bb839f (diff) | |
uapi: export PROCFS_ROOT_INO
The root inode of /proc having a fixed inode number has been part of the
core kernel ABI since its inception, and recently some userspace
programs (mainly container runtimes) have started to explicitly depend
on this behaviour.
The main reason this is useful to userspace is that by checking that a
suspect /proc handle has fstype PROC_SUPER_MAGIC and is PROCFS_ROOT_INO,
they can then use openat2(RESOLVE_{NO_{XDEV,MAGICLINK},BENEATH}) to
ensure that there isn't a bind-mount that replaces some procfs file with
a different one. This kind of attack has lead to security issues in
container runtimes in the past (such as CVE-2019-19921) and libraries
like libpathrs[1] use this feature of procfs to provide safe procfs
handling functions.
There was also some trailing whitespace in the "struct proc_dir_entry"
initialiser, so fix that up as well.
[1]: https://github.com/openSUSE/libpathrs
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/20250708-uapi-procfs-root-ino-v1-1-6ae61e97c79b@cyphar.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/proc/root.c')
| -rw-r--r-- | fs/proc/root.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/fs/proc/root.c b/fs/proc/root.c index 06a297a27ba3..ed86ac710384 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -363,12 +363,12 @@ static const struct inode_operations proc_root_inode_operations = { * This is the root "inode" in the /proc tree.. */ struct proc_dir_entry proc_root = { - .low_ino = PROC_ROOT_INO, - .namelen = 5, - .mode = S_IFDIR | S_IRUGO | S_IXUGO, - .nlink = 2, + .low_ino = PROCFS_ROOT_INO, + .namelen = 5, + .mode = S_IFDIR | S_IRUGO | S_IXUGO, + .nlink = 2, .refcnt = REFCOUNT_INIT(1), - .proc_iops = &proc_root_inode_operations, + .proc_iops = &proc_root_inode_operations, .proc_dir_ops = &proc_root_operations, .parent = &proc_root, .subdir = RB_ROOT, |