From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.hallyn.com (mail.hallyn.com [178.63.66.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF3963232; Thu, 28 Nov 2024 16:34:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.63.66.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732811704; cv=none; b=gR+pyEzVXTt8U5tdeX46ZxD4MPNUH+pK1QX2UToG53lFA6FOtNVK7mLDQ6KzNYNwadn5s5+VSY9qnGunE2k9Keuk+savPu/GUMWmeLtVYr/QdbZraqmUpRLPDPbaTfVVuDlnhDaAb6IBGWDxbQWYuuNtLlXI2c3Vmz291xMNYJg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732811704; c=relaxed/simple; bh=XAnd9478s0HowzAfLuv/IXO/8gg+Bf3Fpu4rBUJ3NyM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=le1SvshiNUFo0NWAqqpCPEJTb3dAcFJBSvKa9tTz6Ctcgb6r2bCf0H17epbzxClIg+/57B8Nm1Sm53kmRafnrZfPy68/0pUGD/NYgGZ/LF2nUj71cD4FcreS1i9so5kjxVd0+vMUklVUSjYvSz+3CZi4wCt5whpHatxq3cfWyXI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=hallyn.com; spf=pass smtp.mailfrom=mail.hallyn.com; arc=none smtp.client-ip=178.63.66.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=hallyn.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mail.hallyn.com Received: by mail.hallyn.com (Postfix, from userid 1001) id E85C355E; Thu, 28 Nov 2024 10:34:52 -0600 (CST) Date: Thu, 28 Nov 2024 10:34:52 -0600 From: "Serge E. Hallyn" To: Jordan Rome Cc: linux-security-module@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Andrii Nakryiko , Kernel Team , Serge Hallyn , Yonghong Song , Linus Torvalds Subject: Re: [v7] security: add trace event for cap_capable Message-ID: <20241128163452.GA40476@mail.hallyn.com> References: <20241128153733.1542817-1-linux@jordanrome.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241128153733.1542817-1-linux@jordanrome.com> On Thu, Nov 28, 2024 at 07:37:33AM -0800, Jordan Rome wrote: > In cases where we want a stable way to observe/trace > cap_capable (e.g. protection from inlining and API updates) > add a tracepoint that passes: > - The credentials used > - The user namespace of the resource being accessed > - The user namespace in which the credential provides the > capability to access the targeted resource > - The capability to check for > - Bitmask of options defined in include/linux/security.h > - The return value of the check > > Signed-off-by: Jordan Rome > --- > MAINTAINERS | 1 + > include/trace/events/capability.h | 60 +++++++++++++++++++++++++++++++ > security/commoncap.c | 57 +++++++++++++++++++---------- > 3 files changed, 100 insertions(+), 18 deletions(-) > create mode 100644 include/trace/events/capability.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index f870842fad9c..b90df58f6030 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -5103,6 +5103,7 @@ M: Serge Hallyn > L: linux-security-module@vger.kernel.org > S: Supported > F: include/linux/capability.h > +F: include/trace/events/capability.h > F: include/uapi/linux/capability.h > F: kernel/capability.c > F: security/commoncap.c > diff --git a/include/trace/events/capability.h b/include/trace/events/capability.h > new file mode 100644 > index 000000000000..65311c2652f7 > --- /dev/null > +++ b/include/trace/events/capability.h > @@ -0,0 +1,60 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#undef TRACE_SYSTEM > +#define TRACE_SYSTEM capability > + > +#if !defined(_TRACE_CAPABILITY_H) || defined(TRACE_HEADER_MULTI_READ) > +#define _TRACE_CAPABILITY_H > + > +#include > +#include > +#include > + > +/** > + * cap_capable - called after it's determined if a task has a particular > + * effective capability > + * > + * @cred: The credentials used > + * @target_ns: The user namespace of the resource being accessed > + * @capable_ns: The user namespace in which the credential provides the > + * capability to access the targeted resource. > + * This will be NULL if ret is not 0. > + * @cap: The capability to check for > + * @opts: Bitmask of options defined in include/linux/security.h > + * @ret: The return value of the check: 0 if it does, -ve if it does not > + * > + * Allows to trace calls to cap_capable in commoncap.c > + */ > +TRACE_EVENT(cap_capable, > + > + TP_PROTO(const struct cred *cred, struct user_namespace *target_ns, > + const struct user_namespace *capable_ns, int cap, unsigned int opts, int ret), Hi, you're still sending opts in here. Will that really be helpful for your use case, given that cap_capable() ignores it as Linus pointed out? > + > + TP_ARGS(cred, target_ns, capable_ns, cap, opts, ret), > + > + TP_STRUCT__entry( > + __field(const struct cred *, cred) > + __field(struct user_namespace *, target_ns) > + __field(const struct user_namespace *, capable_ns) > + __field(int, cap) > + __field(unsigned int, opts) > + __field(int, ret) > + ), > + > + TP_fast_assign( > + __entry->cred = cred; > + __entry->target_ns = target_ns; > + __entry->capable_ns = ret == 0 ? capable_ns : NULL; > + __entry->cap = cap; > + __entry->opts = opts; > + __entry->ret = ret; > + ), > + > + TP_printk("cred %p, target_ns %p, capable_ns %p, cap %d, opts %u, ret %d", > + __entry->cred, __entry->target_ns, __entry->capable_ns, __entry->cap, > + __entry->opts, __entry->ret) > +); > + > +#endif /* _TRACE_CAPABILITY_H */ > + > +/* This part must be outside protection */ > +#include > diff --git a/security/commoncap.c b/security/commoncap.c > index cefad323a0b1..9fa9aba3961d 100644 > --- a/security/commoncap.c > +++ b/security/commoncap.c > @@ -27,6 +27,9 @@ > #include > #include > > +#define CREATE_TRACE_POINTS > +#include > + > /* > * If a non-root user executes a setuid-root binary in > * !secure(SECURE_NOROOT) mode, then we raise capabilities. > @@ -50,24 +53,17 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) > } > > /** > - * cap_capable - Determine whether a task has a particular effective capability > - * @cred: The credentials to use > - * @targ_ns: The user namespace in which we need the capability > - * @cap: The capability to check for > - * @opts: Bitmask of options defined in include/linux/security.h > + * cap_capable_helper - Determine whether a task has a particular effective > + * capability. > * > - * Determine whether the nominated task has the specified capability amongst > - * its effective set, returning 0 if it does, -ve if it does not. > - * > - * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() > - * and has_capability() functions. That is, it has the reverse semantics: > - * cap_has_capability() returns 0 when a task has a capability, but the > - * kernel's capable() and has_capability() returns 1 for this case. > + * See cap_capable for more details. > */ > -int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > - int cap, unsigned int opts) > +static inline int cap_capable_helper(const struct cred *cred, > + struct user_namespace *target_ns, > + const struct user_namespace *cred_ns, > + int cap) > { > - struct user_namespace *ns = targ_ns; > + struct user_namespace *ns = target_ns; > > /* See if cred has the capability in the target user namespace > * by examining the target user namespace and all of the target > @@ -75,21 +71,21 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > */ > for (;;) { > /* Do we have the necessary capabilities? */ > - if (ns == cred->user_ns) > + if (likely(ns == cred_ns)) > return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; > > /* > * If we're already at a lower level than we're looking for, > * we're done searching. > */ > - if (ns->level <= cred->user_ns->level) > + if (ns->level <= cred_ns->level) > return -EPERM; > > /* > * The owner of the user namespace in the parent of the > * user namespace has all caps. > */ > - if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) > + if ((ns->parent == cred_ns) && uid_eq(ns->owner, cred->euid)) > return 0; > > /* > @@ -102,6 +98,31 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, > /* We never get here */ > } > > +/** > + * cap_capable - Determine whether a task has a particular effective capability > + * @cred: The credentials to use > + * @target_ns: The user namespace of the resource being accessed > + * @cap: The capability to check for > + * @opts: Bitmask of options defined in include/linux/security.h > + * > + * Determine whether the nominated task has the specified capability amongst > + * its effective set, returning 0 if it does, -ve if it does not. > + * > + * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() > + * and has_capability() functions. That is, it has the reverse semantics: > + * cap_has_capability() returns 0 when a task has a capability, but the > + * kernel's capable() and has_capability() returns 1 for this case. > + */ > +int cap_capable(const struct cred *cred, struct user_namespace *target_ns, > + int cap, unsigned int opts) > +{ > + const struct user_namespace *cred_ns = cred->user_ns; > + int ret = cap_capable_helper(cred, target_ns, cred_ns, cap); > + > + trace_cap_capable(cred, target_ns, cred_ns, cap, opts, ret); > + return ret; > +} > + > /** > * cap_settime - Determine whether the current process may set the system clock > * @ts: The time to set > -- > 2.43.5 >