diff options
| author | Christian Brauner <brauner@kernel.org> | 2025-02-04 14:51:20 +0100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-02-07 10:27:28 +0100 |
| commit | 091ee63e36e8289f9067f659a48d497911e49d6f (patch) | |
| tree | aee259fb7699267618b8b6fc07cb8d355828ed9e /fs/pidfs.c | |
| parent | ec6164adc73e57c4c43b37682cae1d5c9ad40ca1 (diff) | |
pidfs: improve ioctl handling
Pidfs supports extensible and non-extensible ioctls. The extensible
ioctls need to check for the ioctl number itself not just the ioctl
command otherwise both backward- and forward compatibility are broken.
The pidfs ioctl handler also needs to look at the type of the ioctl
command to guard against cases where "[...] a daemon receives some
random file descriptor from a (potentially less privileged) client and
expects the FD to be of some specific type, it might call ioctl() on
this FD with some type-specific command and expect the call to fail if
the FD is of the wrong type; but due to the missing type check, the
kernel instead performs some action that userspace didn't expect."
(cf. [1]]
Link: https://lore.kernel.org/r/20250204-work-pidfs-ioctl-v1-1-04987d239575@kernel.org
Link: https://lore.kernel.org/r/CAG48ez2K9A5GwtgqO31u9ZL292we8ZwAA=TJwwEv7wRuJ3j4Lw@mail.gmail.com [1]
Fixes: 8ce352818820 ("pidfs: check for valid ioctl commands")
Acked-by: Luca Boccassi <luca.boccassi@gmail.com>
Reported-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org # v6.13; please backport with 8ce352818820 ("pidfs: check for valid ioctl commands")
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/pidfs.c')
| -rw-r--r-- | fs/pidfs.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/fs/pidfs.c b/fs/pidfs.c index 049352f973de..63f9699ebac3 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -287,7 +287,6 @@ static bool pidfs_ioctl_valid(unsigned int cmd) switch (cmd) { case FS_IOC_GETVERSION: case PIDFD_GET_CGROUP_NAMESPACE: - case PIDFD_GET_INFO: case PIDFD_GET_IPC_NAMESPACE: case PIDFD_GET_MNT_NAMESPACE: case PIDFD_GET_NET_NAMESPACE: @@ -300,6 +299,17 @@ static bool pidfs_ioctl_valid(unsigned int cmd) return true; } + /* Extensible ioctls require some more careful checks. */ + switch (_IOC_NR(cmd)) { + case _IOC_NR(PIDFD_GET_INFO): + /* + * Try to prevent performing a pidfd ioctl when someone + * erronously mistook the file descriptor for a pidfd. + * This is not perfect but will catch most cases. + */ + return (_IOC_TYPE(cmd) == _IOC_TYPE(PIDFD_GET_INFO)); + } + return false; } |