On 2019-03-18 07:10, Neil Horman wrote:
> On Fri, Mar 15, 2019 at 02:29:51PM -0400, Richard Guy Briggs wrote:
> > Add support for reading the audit container identifier from the proc
> > filesystem.
> >
> > This is a read from the proc entry of the form
> > /proc/PID/audit_containerid where PID is the process ID of the task
> > whose audit container identifier is sought.
> >
> > The read expects up to a u64 value (unset: 18446744073709551615).
> >
> > This read requires CAP_AUDIT_CONTROL.
> >
> > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> > Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
> > ---
> > fs/proc/base.c | 23 +++++++++++++++++++++--
> > 1 file changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/proc/base.c b/fs/proc/base.c
> > index 2505c46c8701..0b833cbdf5b6 100644
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -1295,6 +1295,24 @@ static ssize_t proc_sessionid_read(struct file * file, char __user * buf,
> > .llseek = generic_file_llseek,
> > };
> >
> > +static ssize_t proc_contid_read(struct file *file, char __user *buf,
> > + size_t count, loff_t *ppos)
> > +{
> > + struct inode *inode = file_inode(file);
> > + struct task_struct *task = get_proc_task(inode);
> > + ssize_t length;
> > + char tmpbuf[TMPBUFLEN*2];
> > +
> Sorry, didn't notice this previously, but..
> Why *2 here? Its not wrong per-se, but would it be better to just change
> TMPBUFLEN to be 22 bytes unilaterally? Its only ever used on stack calls that
> arent that deep, and then you won't have to think about adjusting this call site
> if you ever change the value of TMPBUFLEN in the future.
TMPBUFLEN is 11 to accomodate a decimal representation of a u32 with
terminating NULL. Since the contid is a u64, it was least disruptive
and made sense to me to just double it. I could define a TMPBUFLEN2 to
be 21 if you prefer?
> I'm fine with doing this in another patch later, but it seems like a worthwhile
> cleanup
>
> functionality looks good beyond that nit.
>
> > + if (!task)
> > + return -ESRCH;
> > + /* if we don't have caps, reject */
> > + if (!capable(CAP_AUDIT_CONTROL))
> > + return -EPERM;
> > + length = scnprintf(tmpbuf, TMPBUFLEN*2, "%llu", audit_get_contid(task));
> > + put_task_struct(task);
> > + return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
> > +}
> > +
> > static ssize_t proc_contid_write(struct file *file, const char __user *buf,
> > size_t count, loff_t *ppos)
> > {
> > @@ -1325,6 +1343,7 @@ static ssize_t proc_contid_write(struct file *file, const char __user *buf,
> > }
> >
> > static const struct file_operations proc_contid_operations = {
> > + .read = proc_contid_read,
> > .write = proc_contid_write,
> > .llseek = generic_file_llseek,
> > };
> > @@ -3039,7 +3058,7 @@ static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
> > #ifdef CONFIG_AUDIT
> > REG("loginuid", S_IWUSR|S_IRUGO, proc_loginuid_operations),
> > REG("sessionid", S_IRUGO, proc_sessionid_operations),
> > - REG("audit_containerid", S_IWUSR, proc_contid_operations),
> > + REG("audit_containerid", S_IWUSR|S_IRUSR, proc_contid_operations),
> > #endif
> > #ifdef CONFIG_FAULT_INJECTION
> > REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
> > @@ -3428,7 +3447,7 @@ static int proc_tid_comm_permission(struct inode *inode, int mask)
> > #ifdef CONFIG_AUDIT
> > REG("loginuid", S_IWUSR|S_IRUGO, proc_loginuid_operations),
> > REG("sessionid", S_IRUGO, proc_sessionid_operations),
> > - REG("audit_containerid", S_IWUSR, proc_contid_operations),
> > + REG("audit_containerid", S_IWUSR|S_IRUSR, proc_contid_operations),
> > #endif
> > #ifdef CONFIG_FAULT_INJECTION
> > REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
> > --
> > 1.8.3.1
> >
> >
> Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
>
- RGB
--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635
