* [PATCH v1 0/2] Fix misuse of security_capable()
@ 2020-10-30 12:38 Mickaël Salaün
2020-10-30 12:38 ` [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability Mickaël Salaün
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Mickaël Salaün @ 2020-10-30 12:38 UTC (permalink / raw)
To: Christian Brauner, Jann Horn, Kees Cook, Oleg Nesterov
Cc: Mickaël Salaün, Eric Paris, James Morris,
Serge E . Hallyn, Tyler Hicks, Will Drewry, linux-kernel, stable
This series replaces all the use of security_capable(current_cred(),
...) with ns_capable{,_noaudit}() which set PF_SUPERPRIV.
This initially come from a review of Landlock by Jann Horn:
https://lore.kernel.org/lkml/CAG48ez1FQVkt78129WozBwFbVhAPyAr9oJAHFHAbbNxEBr9h1g@mail.gmail.com/
Mickaël Salaün (2):
ptrace: Set PF_SUPERPRIV when checking capability
seccomp: Set PF_SUPERPRIV when checking capability
kernel/ptrace.c | 18 ++++++------------
kernel/seccomp.c | 5 ++---
2 files changed, 8 insertions(+), 15 deletions(-)
base-commit: 3650b228f83adda7e5ee532e2b90429c03f7b9ec
--
2.28.0
^ permalink raw reply [flat|nested] 8+ messages in thread* [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability 2020-10-30 12:38 [PATCH v1 0/2] Fix misuse of security_capable() Mickaël Salaün @ 2020-10-30 12:38 ` Mickaël Salaün 2020-10-30 15:47 ` Jann Horn 2020-10-30 12:38 ` [PATCH v1 2/2] seccomp: " Mickaël Salaün 2020-11-17 21:08 ` [PATCH v1 0/2] Fix misuse of security_capable() Kees Cook 2 siblings, 1 reply; 8+ messages in thread From: Mickaël Salaün @ 2020-10-30 12:38 UTC (permalink / raw) To: Christian Brauner, Jann Horn, Kees Cook, Oleg Nesterov Cc: Mickaël Salaün, Eric Paris, James Morris, Serge E . Hallyn, Tyler Hicks, Will Drewry, linux-kernel, stable, Mickaël Salaün From: Mickaël Salaün <mic@linux.microsoft.com> Commit 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") replaced the use of ns_capable() with has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV. Commit 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with security_capable(), which doesn't set PF_SUPERPRIV neither. Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a new ns_capable_noaudit() helper is available. Let's use it! As a result, the signature of ptrace_has_cap() is restored to its original one. Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Eric Paris <eparis@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Serge E. Hallyn <serge@hallyn.com> Cc: Tyler Hicks <tyhicks@linux.microsoft.com> Cc: stable@vger.kernel.org Fixes: 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") Fixes: 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> --- kernel/ptrace.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 43d6179508d6..aa3c2fd6e41b 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -264,23 +264,17 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) return ret; } -static bool ptrace_has_cap(const struct cred *cred, struct user_namespace *ns, - unsigned int mode) +static bool ptrace_has_cap(struct user_namespace *ns, unsigned int mode) { - int ret; - if (mode & PTRACE_MODE_NOAUDIT) - ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NOAUDIT); - else - ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NONE); - - return ret == 0; + return ns_capable_noaudit(ns, CAP_SYS_PTRACE); + return ns_capable(ns, CAP_SYS_PTRACE); } /* Returns 0 on success, -errno on denial. */ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) { - const struct cred *cred = current_cred(), *tcred; + const struct cred *const cred = current_cred(), *tcred; struct mm_struct *mm; kuid_t caller_uid; kgid_t caller_gid; @@ -326,7 +320,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) gid_eq(caller_gid, tcred->sgid) && gid_eq(caller_gid, tcred->gid)) goto ok; - if (ptrace_has_cap(cred, tcred->user_ns, mode)) + if (ptrace_has_cap(tcred->user_ns, mode)) goto ok; rcu_read_unlock(); return -EPERM; @@ -345,7 +339,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) mm = task->mm; if (mm && ((get_dumpable(mm) != SUID_DUMP_USER) && - !ptrace_has_cap(cred, mm->user_ns, mode))) + !ptrace_has_cap(mm->user_ns, mode))) return -EPERM; return security_ptrace_access_check(task, mode); -- 2.28.0 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability 2020-10-30 12:38 ` [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability Mickaël Salaün @ 2020-10-30 15:47 ` Jann Horn 2020-10-30 16:06 ` Mickaël Salaün 0 siblings, 1 reply; 8+ messages in thread From: Jann Horn @ 2020-10-30 15:47 UTC (permalink / raw) To: Mickaël Salaün Cc: Christian Brauner, Kees Cook, Oleg Nesterov, Eric Paris, James Morris, Serge E . Hallyn, Tyler Hicks, Will Drewry, kernel list, stable, Mickaël Salaün On Fri, Oct 30, 2020 at 1:39 PM Mickaël Salaün <mic@digikod.net> wrote: > Commit 69f594a38967 ("ptrace: do not audit capability check when outputing > /proc/pid/stat") replaced the use of ns_capable() with > has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV. > > Commit 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in > ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with > security_capable(), which doesn't set PF_SUPERPRIV neither. > > Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a > new ns_capable_noaudit() helper is available. Let's use it! > > As a result, the signature of ptrace_has_cap() is restored to its original one. > > Cc: Christian Brauner <christian.brauner@ubuntu.com> > Cc: Eric Paris <eparis@redhat.com> > Cc: Jann Horn <jannh@google.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Oleg Nesterov <oleg@redhat.com> > Cc: Serge E. Hallyn <serge@hallyn.com> > Cc: Tyler Hicks <tyhicks@linux.microsoft.com> > Cc: stable@vger.kernel.org > Fixes: 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") > Fixes: 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") > Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Yeah... I guess this makes sense. (We'd have to undo or change it if we ever end up needing to use a different set of credentials, e.g. from ->f_cred, but I guess that's really something we should avoid anyway.) Reviewed-by: Jann Horn <jannh@google.com> with one nit: [...] > /* Returns 0 on success, -errno on denial. */ > static int __ptrace_may_access(struct task_struct *task, unsigned int mode) > { > - const struct cred *cred = current_cred(), *tcred; > + const struct cred *const cred = current_cred(), *tcred; This is an unrelated change, and almost no kernel code marks local pointer variables as "const". I would drop this change from the patch. > struct mm_struct *mm; > kuid_t caller_uid; > kgid_t caller_gid; ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability 2020-10-30 15:47 ` Jann Horn @ 2020-10-30 16:06 ` Mickaël Salaün 2020-10-30 18:00 ` Jann Horn 0 siblings, 1 reply; 8+ messages in thread From: Mickaël Salaün @ 2020-10-30 16:06 UTC (permalink / raw) To: Jann Horn Cc: Christian Brauner, Kees Cook, Oleg Nesterov, Eric Paris, James Morris, Serge E . Hallyn, Tyler Hicks, Will Drewry, kernel list, stable, Mickaël Salaün On 30/10/2020 16:47, Jann Horn wrote: > On Fri, Oct 30, 2020 at 1:39 PM Mickaël Salaün <mic@digikod.net> wrote: >> Commit 69f594a38967 ("ptrace: do not audit capability check when outputing >> /proc/pid/stat") replaced the use of ns_capable() with >> has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV. >> >> Commit 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in >> ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with >> security_capable(), which doesn't set PF_SUPERPRIV neither. >> >> Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a >> new ns_capable_noaudit() helper is available. Let's use it! >> >> As a result, the signature of ptrace_has_cap() is restored to its original one. >> >> Cc: Christian Brauner <christian.brauner@ubuntu.com> >> Cc: Eric Paris <eparis@redhat.com> >> Cc: Jann Horn <jannh@google.com> >> Cc: Kees Cook <keescook@chromium.org> >> Cc: Oleg Nesterov <oleg@redhat.com> >> Cc: Serge E. Hallyn <serge@hallyn.com> >> Cc: Tyler Hicks <tyhicks@linux.microsoft.com> >> Cc: stable@vger.kernel.org >> Fixes: 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") >> Fixes: 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> > > Yeah... I guess this makes sense. (We'd have to undo or change it if > we ever end up needing to use a different set of credentials, e.g. > from ->f_cred, but I guess that's really something we should avoid > anyway.) > > Reviewed-by: Jann Horn <jannh@google.com> > > with one nit: > > > [...] >> /* Returns 0 on success, -errno on denial. */ >> static int __ptrace_may_access(struct task_struct *task, unsigned int mode) >> { >> - const struct cred *cred = current_cred(), *tcred; >> + const struct cred *const cred = current_cred(), *tcred; > > This is an unrelated change, and almost no kernel code marks local > pointer variables as "const". I would drop this change from the patch. This give guarantee that the cred variable will not be used for something else than current_cred(), which kinda prove that this patch doesn't change the behavior of __ptrace_may_access() by not using cred in ptrace_has_cap(). It doesn't hurt and I think it could be useful to spot issues when backporting. > >> struct mm_struct *mm; >> kuid_t caller_uid; >> kgid_t caller_gid; ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability 2020-10-30 16:06 ` Mickaël Salaün @ 2020-10-30 18:00 ` Jann Horn 0 siblings, 0 replies; 8+ messages in thread From: Jann Horn @ 2020-10-30 18:00 UTC (permalink / raw) To: Mickaël Salaün Cc: Christian Brauner, Kees Cook, Oleg Nesterov, Eric Paris, James Morris, Serge E . Hallyn, Tyler Hicks, Will Drewry, kernel list, stable, Mickaël Salaün On Fri, Oct 30, 2020 at 5:06 PM Mickaël Salaün <mic@digikod.net> wrote: > On 30/10/2020 16:47, Jann Horn wrote: > > On Fri, Oct 30, 2020 at 1:39 PM Mickaël Salaün <mic@digikod.net> wrote: > >> Commit 69f594a38967 ("ptrace: do not audit capability check when outputing > >> /proc/pid/stat") replaced the use of ns_capable() with > >> has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV. > >> > >> Commit 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in > >> ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with > >> security_capable(), which doesn't set PF_SUPERPRIV neither. > >> > >> Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a > >> new ns_capable_noaudit() helper is available. Let's use it! > >> > >> As a result, the signature of ptrace_has_cap() is restored to its original one. > >> > >> Cc: Christian Brauner <christian.brauner@ubuntu.com> > >> Cc: Eric Paris <eparis@redhat.com> > >> Cc: Jann Horn <jannh@google.com> > >> Cc: Kees Cook <keescook@chromium.org> > >> Cc: Oleg Nesterov <oleg@redhat.com> > >> Cc: Serge E. Hallyn <serge@hallyn.com> > >> Cc: Tyler Hicks <tyhicks@linux.microsoft.com> > >> Cc: stable@vger.kernel.org > >> Fixes: 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") > >> Fixes: 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") > >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> > > > > Yeah... I guess this makes sense. (We'd have to undo or change it if > > we ever end up needing to use a different set of credentials, e.g. > > from ->f_cred, but I guess that's really something we should avoid > > anyway.) > > > > Reviewed-by: Jann Horn <jannh@google.com> > > > > with one nit: > > > > > > [...] > >> /* Returns 0 on success, -errno on denial. */ > >> static int __ptrace_may_access(struct task_struct *task, unsigned int mode) > >> { > >> - const struct cred *cred = current_cred(), *tcred; > >> + const struct cred *const cred = current_cred(), *tcred; > > > > This is an unrelated change, and almost no kernel code marks local > > pointer variables as "const". I would drop this change from the patch. > > This give guarantee that the cred variable will not be used for > something else than current_cred(), which kinda prove that this patch > doesn't change the behavior of __ptrace_may_access() by not using cred > in ptrace_has_cap(). It doesn't hurt and I think it could be useful to > spot issues when backporting. And it might require an extra fixup while backporting because the next line is different and that might cause the patch to not apply. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH v1 2/2] seccomp: Set PF_SUPERPRIV when checking capability 2020-10-30 12:38 [PATCH v1 0/2] Fix misuse of security_capable() Mickaël Salaün 2020-10-30 12:38 ` [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability Mickaël Salaün @ 2020-10-30 12:38 ` Mickaël Salaün 2020-10-30 15:34 ` Jann Horn 2020-11-17 21:08 ` [PATCH v1 0/2] Fix misuse of security_capable() Kees Cook 2 siblings, 1 reply; 8+ messages in thread From: Mickaël Salaün @ 2020-10-30 12:38 UTC (permalink / raw) To: Christian Brauner, Jann Horn, Kees Cook, Oleg Nesterov Cc: Mickaël Salaün, Eric Paris, James Morris, Serge E . Hallyn, Tyler Hicks, Will Drewry, linux-kernel, stable, Mickaël Salaün From: Mickaël Salaün <mic@linux.microsoft.com> Replace the use of security_capable(current_cred(), ...) with ns_capable_noaudit() which set PF_SUPERPRIV. Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a new ns_capable_noaudit() helper is available. Let's use it! Cc: Jann Horn <jannh@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Tyler Hicks <tyhicks@linux.microsoft.com> Cc: Will Drewry <wad@chromium.org> Cc: stable@vger.kernel.org Fixes: e2cfabdfd075 ("seccomp: add system call filtering using BPF") Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> --- kernel/seccomp.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 8ad7a293255a..53a7d1512dd7 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -38,7 +38,7 @@ #include <linux/filter.h> #include <linux/pid.h> #include <linux/ptrace.h> -#include <linux/security.h> +#include <linux/capability.h> #include <linux/tracehook.h> #include <linux/uaccess.h> #include <linux/anon_inodes.h> @@ -558,8 +558,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) * behavior of privileged children. */ if (!task_no_new_privs(current) && - security_capable(current_cred(), current_user_ns(), - CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) != 0) + !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN)) return ERR_PTR(-EACCES); /* Allocate a new seccomp_filter */ -- 2.28.0 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v1 2/2] seccomp: Set PF_SUPERPRIV when checking capability 2020-10-30 12:38 ` [PATCH v1 2/2] seccomp: " Mickaël Salaün @ 2020-10-30 15:34 ` Jann Horn 0 siblings, 0 replies; 8+ messages in thread From: Jann Horn @ 2020-10-30 15:34 UTC (permalink / raw) To: Mickaël Salaün Cc: Christian Brauner, Kees Cook, Oleg Nesterov, Eric Paris, James Morris, Serge E . Hallyn, Tyler Hicks, Will Drewry, kernel list, stable, Mickaël Salaün On Fri, Oct 30, 2020 at 1:39 PM Mickaël Salaün <mic@digikod.net> wrote: > Replace the use of security_capable(current_cred(), ...) with > ns_capable_noaudit() which set PF_SUPERPRIV. > > Since commit 98f368e9e263 ("kernel: Add noaudit variant of > ns_capable()"), a new ns_capable_noaudit() helper is available. Let's > use it! > > Cc: Jann Horn <jannh@google.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Tyler Hicks <tyhicks@linux.microsoft.com> > Cc: Will Drewry <wad@chromium.org> > Cc: stable@vger.kernel.org > Fixes: e2cfabdfd075 ("seccomp: add system call filtering using BPF") > Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> Reviewed-by: Jann Horn <jannh@google.com> ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v1 0/2] Fix misuse of security_capable() 2020-10-30 12:38 [PATCH v1 0/2] Fix misuse of security_capable() Mickaël Salaün 2020-10-30 12:38 ` [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability Mickaël Salaün 2020-10-30 12:38 ` [PATCH v1 2/2] seccomp: " Mickaël Salaün @ 2020-11-17 21:08 ` Kees Cook 2 siblings, 0 replies; 8+ messages in thread From: Kees Cook @ 2020-11-17 21:08 UTC (permalink / raw) To: Oleg Nesterov, Christian Brauner, Jann Horn, Mickaël Salaün Cc: Kees Cook, Eric Paris, Will Drewry, Serge E . Hallyn, stable, Tyler Hicks, James Morris, linux-kernel On Fri, 30 Oct 2020 13:38:47 +0100, Mickaël Salaün wrote: > This series replaces all the use of security_capable(current_cred(), > ...) with ns_capable{,_noaudit}() which set PF_SUPERPRIV. > > This initially come from a review of Landlock by Jann Horn: > https://lore.kernel.org/lkml/CAG48ez1FQVkt78129WozBwFbVhAPyAr9oJAHFHAbbNxEBr9h1g@mail.gmail.com/ > > Mickaël Salaün (2): > ptrace: Set PF_SUPERPRIV when checking capability > seccomp: Set PF_SUPERPRIV when checking capability > > [...] Applied to for-linus/seccomp, thanks! [1/2] ptrace: Set PF_SUPERPRIV when checking capability https://git.kernel.org/kees/c/cf23705244c9 [2/2] seccomp: Set PF_SUPERPRIV when checking capability https://git.kernel.org/kees/c/fb14528e4436 -- Kees Cook ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-11-17 21:09 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-10-30 12:38 [PATCH v1 0/2] Fix misuse of security_capable() Mickaël Salaün 2020-10-30 12:38 ` [PATCH v1 1/2] ptrace: Set PF_SUPERPRIV when checking capability Mickaël Salaün 2020-10-30 15:47 ` Jann Horn 2020-10-30 16:06 ` Mickaël Salaün 2020-10-30 18:00 ` Jann Horn 2020-10-30 12:38 ` [PATCH v1 2/2] seccomp: " Mickaël Salaün 2020-10-30 15:34 ` Jann Horn 2020-11-17 21:08 ` [PATCH v1 0/2] Fix misuse of security_capable() Kees Cook
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