| Message ID | 1488292508-32506-1-git-send-email-sds@tycho.nsa.gov (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Tue, Feb 28, 2017 at 9:35 AM, Stephen Smalley <sds@tycho.nsa.gov> wrote: > commit 79bcf325e6b32b3c ("prlimit,security,selinux: add a security hook > for prlimit") introduced a security hook for prlimit() and implemented it > for SELinux. However, if prlimit() is called with NULL arguments for both > the new limit and the old limit, then the hook is called with 0 for the > read/write flags, since the prlimit() will neither read nor write the > process' limits. This would in turn lead to calling avc_has_perm() with 0 > for the requested permissions, which triggers a BUG_ON() in > avc_has_perm_noaudit() since the kernel should never be invoking > avc_has_perm() with no permissions. Fix this in the SELinux hook by > returning immediately if the flags are 0. Arguably prlimit64() itself > ought to return immediately if both old_rlim and new_rlim are NULL since > it is effectively a no-op in that case. > > Reported by the lkp-robot based on trinity testing. > > Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> > --- > security/selinux/hooks.c | 2 ++ > 1 file changed, 2 insertions(+) James, I was going to merge this patch but upon closer inspection it appears that you never sent 79bcf325e6b32b3c to Linux, it is sitting in your next-queue branch. What is the plan for your next-queue branch, are you going to merge it into your next branch after the merge window closes? If so, feel free to add my ack. Acked-by: Paul Moore <paul@paul-moore.com> > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 4a80bd8..af1ff15 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -3922,6 +3922,8 @@ int selinux_task_prlimit(const struct cred *cred, const struct cred *tcred, > { > u32 av = 0; > > + if (!flags) > + return 0; > if (flags & LSM_PRLIMIT_WRITE) > av |= PROCESS__SETRLIMIT; > if (flags & LSM_PRLIMIT_READ) > -- > 2.7.4 >
On Tue, 28 Feb 2017, Paul Moore wrote: > I was going to merge this patch but upon closer inspection it appears > that you never sent 79bcf325e6b32b3c to Linux, it is sitting in your > next-queue branch. What is the plan for your next-queue branch, are > you going to merge it into your next branch after the merge window > closes? If so, feel free to add my ack. Yes, at -rc1. > > Acked-by: Paul Moore <paul@paul-moore.com> Thanks.
On Tue, 28 Feb 2017, Stephen Smalley wrote: > > Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> > --- Applied to git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git#next-queue
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 4a80bd8..af1ff15 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3922,6 +3922,8 @@ int selinux_task_prlimit(const struct cred *cred, const struct cred *tcred, { u32 av = 0; + if (!flags) + return 0; if (flags & LSM_PRLIMIT_WRITE) av |= PROCESS__SETRLIMIT; if (flags & LSM_PRLIMIT_READ)
commit 79bcf325e6b32b3c ("prlimit,security,selinux: add a security hook for prlimit") introduced a security hook for prlimit() and implemented it for SELinux. However, if prlimit() is called with NULL arguments for both the new limit and the old limit, then the hook is called with 0 for the read/write flags, since the prlimit() will neither read nor write the process' limits. This would in turn lead to calling avc_has_perm() with 0 for the requested permissions, which triggers a BUG_ON() in avc_has_perm_noaudit() since the kernel should never be invoking avc_has_perm() with no permissions. Fix this in the SELinux hook by returning immediately if the flags are 0. Arguably prlimit64() itself ought to return immediately if both old_rlim and new_rlim are NULL since it is effectively a no-op in that case. Reported by the lkp-robot based on trinity testing. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> --- security/selinux/hooks.c | 2 ++ 1 file changed, 2 insertions(+)