| Message ID | 20241128153733.1542817-1-linux@jordanrome.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v7] security: add trace event for cap_capable | expand |
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 <linux@jordanrome.com> > --- > 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 <serge@hallyn.com> > 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 <linux/cred.h> > +#include <linux/tracepoint.h> > +#include <linux/user_namespace.h> > + > +/** > + * 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 <trace/define_trace.h> > 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 <linux/mnt_idmapping.h> > #include <uapi/linux/lsm.h> > > +#define CREATE_TRACE_POINTS > +#include <trace/events/capability.h> > + > /* > * 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 >
On Thu, Nov 28, 2024 at 11:34 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > 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 <linux@jordanrome.com> > > --- > > 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 <serge@hallyn.com> > > 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 <linux/cred.h> > > +#include <linux/tracepoint.h> > > +#include <linux/user_namespace.h> > > + > > +/** > > + * 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? > Ah, my bad. I'll remove. > > + > > + 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 <trace/define_trace.h> > > 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 <linux/mnt_idmapping.h> > > #include <uapi/linux/lsm.h> > > > > +#define CREATE_TRACE_POINTS > > +#include <trace/events/capability.h> > > + > > /* > > * 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 > >
diff --git a/MAINTAINERS b/MAINTAINERS index f870842fad9c..b90df58f6030 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5103,6 +5103,7 @@ M: Serge Hallyn <serge@hallyn.com> 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 <linux/cred.h> +#include <linux/tracepoint.h> +#include <linux/user_namespace.h> + +/** + * 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), + + 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 <trace/define_trace.h> 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 <linux/mnt_idmapping.h> #include <uapi/linux/lsm.h> +#define CREATE_TRACE_POINTS +#include <trace/events/capability.h> + /* * 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
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 <linux@jordanrome.com> --- 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 -- 2.43.5