On Mon, Jul 12, 2021 at 7:48 PM Austin Kim <austindh.kim@xxxxxxxxx> wrote: > From: Austin Kim <austin.kim@xxxxxxx> > > It is possible for audit_log_start() to return NULL on error. > So add exception handling for possible NULL audit buffers where > return value can be handled from callers. Hi. The patch looks fine to me, but I think the description doesn't tell the full story and I'm worried that people might misunderstand why this patch is worthwhile. I would suggest you revise the commit description to explain that in these cases it is safe to return early when audit_log_start() returns NULL because the only non-cleanup processing left in these functions is to generate an audit record. Returning early in these cases is a performance optimization and not a correctness issue; the audit_log_*() functions can support being passed a NULL audit_buffer argument. > Signed-off-by: Austin Kim <austin.kim@xxxxxxx> > --- > security/selinux/hooks.c | 4 ++++ > security/selinux/ss/services.c | 2 ++ > 2 files changed, 6 insertions(+) > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index b0032c42333e..9e84e6635f2f 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -3325,6 +3325,8 @@ static int selinux_inode_setxattr(struct user_namespace *mnt_userns, > } > ab = audit_log_start(audit_context(), > GFP_ATOMIC, AUDIT_SELINUX_ERR); > + if (!ab) > + return rc; > audit_log_format(ab, "op=setxattr invalid_context="); > audit_log_n_untrustedstring(ab, value, audit_size); > audit_log_end(ab); > @@ -6552,6 +6554,8 @@ static int selinux_setprocattr(const char *name, void *value, size_t size) > ab = audit_log_start(audit_context(), > GFP_ATOMIC, > AUDIT_SELINUX_ERR); > + if (!ab) > + return error; > audit_log_format(ab, "op=fscreate invalid_context="); > audit_log_n_untrustedstring(ab, value, audit_size); > audit_log_end(ab); > diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c > index d84c77f370dc..e5f1b2757a83 100644 > --- a/security/selinux/ss/services.c > +++ b/security/selinux/ss/services.c > @@ -1673,6 +1673,8 @@ static int compute_sid_handle_invalid_context( > if (context_struct_to_string(policydb, newcontext, &n, &nlen)) > goto out; > ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_SELINUX_ERR); > + if (!ab) > + goto out; > audit_log_format(ab, > "op=security_compute_sid invalid_context="); > /* no need to record the NUL with untrusted strings */ > -- > 2.20.1 -- paul moore www.paul-moore.com
