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SubjectRe: [PATCH v5 3/3] fanotify,audit: Allow audit to use the full permission event response
On 2023-01-09 19:06, Steve Grubb wrote:
> Hello,
>
> Sorry to take so long. Holidays and kernel build problems. However, I have
> built a kernel with these patches. I only have 2 comments. When I use an
> application that expected the old API, meaning it simply does:
>
> response.fd = metadata->fd;
> response.response = reply;
> close(metadata->fd);
> write(fd, &response, sizeof(struct fanotify_response));
>
> I get access denials. Every time. If the program is using the new API and
> sets FAN_INFO, then it works as expected. I'll do some more testing but I
> think there is something wrong in the compatibility path.

I'll have a closer look, because this wasn't the intended behaviour.

> On Monday, December 12, 2022 9:06:11 AM EST Richard Guy Briggs wrote:
> > This patch passes the full response so that the audit function can use all
> > of it. The audit function was updated to log the additional information in
> > the AUDIT_FANOTIFY record.
>
> What I'm seeing is:
>
> type=FANOTIFY msg=audit(01/09/2023 18:43:16.306:366) : resp=deny fan_type=1
> fan_info=313300000000000000000000 subj_trust=0 obj_trust=0
>
> Where fan_info was supposed to be 13 decimal. More below...

Well, it *is* 13 decimal, expressed as a hex-encoded string as was
requested for future-proofing, albeit longer than necessary...

> > Currently the only type of fanotify info that is defined is an audit
> > rule number, but convert it to hex encoding to future-proof the field.
> > Hex encoding suggested by Paul Moore <paul@paul-moore.com>.
> >
> > Sample records:
> > type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1
> > fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY
> > msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=3F subj_trust=2
> > obj_trust=2
> >
> > Suggested-by: Steve Grubb <sgrubb@redhat.com>
> > Link: https://lore.kernel.org/r/3075502.aeNJFYEL58@x2
> > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > ---
> > fs/notify/fanotify/fanotify.c | 3 ++-
> > include/linux/audit.h | 9 +++++----
> > kernel/auditsc.c | 25 ++++++++++++++++++++++---
> > 3 files changed, 29 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> > index 24ec1d66d5a8..29bdd99b29fa 100644
> > --- a/fs/notify/fanotify/fanotify.c
> > +++ b/fs/notify/fanotify/fanotify.c
> > @@ -273,7 +273,8 @@ static int fanotify_get_response(struct fsnotify_group
> > *group,
> >
> > /* Check if the response should be audited */
> > if (event->response & FAN_AUDIT)
> > - audit_fanotify(event->response & ~FAN_AUDIT);
> > + audit_fanotify(event->response & ~FAN_AUDIT,
> > + &event->audit_rule);
> >
> > pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
> > group, event, ret);
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index d6b7d0c7ce43..31086a72e32a 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -14,6 +14,7 @@
> > #include <linux/audit_arch.h>
> > #include <uapi/linux/audit.h>
> > #include <uapi/linux/netfilter/nf_tables.h>
> > +#include <uapi/linux/fanotify.h>
> >
> > #define AUDIT_INO_UNSET ((unsigned long)-1)
> > #define AUDIT_DEV_UNSET ((dev_t)-1)
> > @@ -416,7 +417,7 @@ extern void __audit_log_capset(const struct cred *new,
> > const struct cred *old); extern void __audit_mmap_fd(int fd, int flags);
> > extern void __audit_openat2_how(struct open_how *how);
> > extern void __audit_log_kern_module(char *name);
> > -extern void __audit_fanotify(u32 response);
> > +extern void __audit_fanotify(u32 response, struct
> > fanotify_response_info_audit_rule *friar); extern void
> > __audit_tk_injoffset(struct timespec64 offset);
> > extern void __audit_ntp_log(const struct audit_ntp_data *ad);
> > extern void __audit_log_nfcfg(const char *name, u8 af, unsigned int
> > nentries, @@ -523,10 +524,10 @@ static inline void
> > audit_log_kern_module(char *name) __audit_log_kern_module(name);
> > }
> >
> > -static inline void audit_fanotify(u32 response)
> > +static inline void audit_fanotify(u32 response, struct
> > fanotify_response_info_audit_rule *friar) {
> > if (!audit_dummy_context())
> > - __audit_fanotify(response);
> > + __audit_fanotify(response, friar);
> > }
> >
> > static inline void audit_tk_injoffset(struct timespec64 offset)
> > @@ -679,7 +680,7 @@ static inline void audit_log_kern_module(char *name)
> > {
> > }
> >
> > -static inline void audit_fanotify(u32 response)
> > +static inline void audit_fanotify(u32 response, struct
> > fanotify_response_info_audit_rule *friar) { }
> >
> > static inline void audit_tk_injoffset(struct timespec64 offset)
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index d1fb821de104..8d523066d81f 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -64,6 +64,7 @@
> > #include <uapi/linux/limits.h>
> > #include <uapi/linux/netfilter/nf_tables.h>
> > #include <uapi/linux/openat2.h> // struct open_how
> > +#include <uapi/linux/fanotify.h>
> >
> > #include "audit.h"
> >
> > @@ -2877,10 +2878,28 @@ void __audit_log_kern_module(char *name)
> > context->type = AUDIT_KERN_MODULE;
> > }
> >
> > -void __audit_fanotify(u32 response)
> > +void __audit_fanotify(u32 response, struct
> > fanotify_response_info_audit_rule *friar) {
> > - audit_log(audit_context(), GFP_KERNEL,
> > - AUDIT_FANOTIFY, "resp=%u", response);
> > + struct audit_context *ctx = audit_context();
> > + struct audit_buffer *ab;
> > + char numbuf[12];
> > +
> > + if (friar->hdr.type == FAN_RESPONSE_INFO_NONE) {
> > + audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
> > + "resp=%u fan_type=%u fan_info=3F subj_trust=2
> obj_trust=2",
> > + response, FAN_RESPONSE_INFO_NONE);
> > + return;
> > + }
> > + ab = audit_log_start(ctx, GFP_KERNEL, AUDIT_FANOTIFY);
> > + if (ab) {
> > + audit_log_format(ab, "resp=%u fan_type=%u fan_info=",
> > + response, friar->hdr.type);
> > + snprintf(numbuf, sizeof(numbuf), "%u", friar->rule_number);
> > + audit_log_n_hex(ab, numbuf, sizeof(numbuf));
>
> I don't think it needs to be converted to ascii and then hexencoded. As Paul
> said, probably %X is all we need here.
>
> -Steve
>
>
> > + audit_log_format(ab, " subj_trust=%u obj_trust=%u",
> > + friar->subj_trust, friar->obj_trust);
> > + audit_log_end(ab);
> > + }
> > }
> >
> > void __audit_tk_injoffset(struct timespec64 offset)
>
>
>
>

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

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