| Message ID | 20190116183109.GA21722@beast (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Yama: Check for pid death before checking ancestry | expand |
On Wed, 16 Jan 2019, Kees Cook wrote: > It's possible that a pid has died before we take the rcu lock, in which > case we can't walk the ancestry list as it may be detached. Instead, check > for death first before doing the walk. > > Reported-by: syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com > Fixes: 2d514487faf1 ("security: Yama LSM") > Cc: stable@vger.kernel.org > Suggested-by: Oleg Nesterov <oleg@redhat.com> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > James, can you please send this to Linus in your -fixes tree? Done. > --- > security/yama/yama_lsm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c > index ffda91a4a1aa..02514fe558b4 100644 > --- a/security/yama/yama_lsm.c > +++ b/security/yama/yama_lsm.c > @@ -368,7 +368,9 @@ static int yama_ptrace_access_check(struct task_struct *child, > break; > case YAMA_SCOPE_RELATIONAL: > rcu_read_lock(); > - if (!task_is_descendant(current, child) && > + if (!pid_alive(child)) > + rc = -EPERM; > + if (!rc && !task_is_descendant(current, child) && > !ptracer_exception_found(current, child) && > !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE)) > rc = -EPERM; >
On Thu, 17 Jan 2019, James Morris wrote: > On Wed, 16 Jan 2019, Kees Cook wrote: > > > It's possible that a pid has died before we take the rcu lock, in which > > case we can't walk the ancestry list as it may be detached. Instead, check > > for death first before doing the walk. > > > > Reported-by: syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com > > Fixes: 2d514487faf1 ("security: Yama LSM") > > Cc: stable@vger.kernel.org > > Suggested-by: Oleg Nesterov <oleg@redhat.com> > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > James, can you please send this to Linus in your -fixes tree? > > Done. I mean, queued in that tree. > > > --- > > security/yama/yama_lsm.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c > > index ffda91a4a1aa..02514fe558b4 100644 > > --- a/security/yama/yama_lsm.c > > +++ b/security/yama/yama_lsm.c > > @@ -368,7 +368,9 @@ static int yama_ptrace_access_check(struct task_struct *child, > > break; > > case YAMA_SCOPE_RELATIONAL: > > rcu_read_lock(); > > - if (!task_is_descendant(current, child) && > > + if (!pid_alive(child)) > > + rc = -EPERM; > > + if (!rc && !task_is_descendant(current, child) && > > !ptracer_exception_found(current, child) && > > !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE)) > > rc = -EPERM; > > > >
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index ffda91a4a1aa..02514fe558b4 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -368,7 +368,9 @@ static int yama_ptrace_access_check(struct task_struct *child, break; case YAMA_SCOPE_RELATIONAL: rcu_read_lock(); - if (!task_is_descendant(current, child) && + if (!pid_alive(child)) + rc = -EPERM; + if (!rc && !task_is_descendant(current, child) && !ptracer_exception_found(current, child) && !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE)) rc = -EPERM;
It's possible that a pid has died before we take the rcu lock, in which case we can't walk the ancestry list as it may be detached. Instead, check for death first before doing the walk. Reported-by: syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com Fixes: 2d514487faf1 ("security: Yama LSM") Cc: stable@vger.kernel.org Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- James, can you please send this to Linus in your -fixes tree? --- security/yama/yama_lsm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)