Re: [[PATCH V4]] audit: trigger accompanying records when no rules present

On 2020-09-15 12:18, Paul Moore wrote: > On Thu, Sep 10, 2020 at 11:03 AM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > When there are no audit rules registered, mandatory records (config, > > etc.) are missing their accompanying records (syscall, proctitle, etc.). > > > > This is due to audit context dummy set on syscall entry based on absence > > of rules that signals that no other records are to be printed. > > > > Clear the dummy bit if any record is generated. > > > > The proctitle context and dummy checks are pointless since the > > proctitle record will not be printed if no syscall records are printed. > > > > The fds array is reset to -1 after the first syscall to indicate it > > isn't valid any more, but was never set to -1 when the context was > > allocated to indicate it wasn't yet valid. > > > > The audit_inode* functions can be called without going through > > getname_flags() or getname_kernel() that sets audit_names and cwd, so > > set the cwd if it has not already been done so due to audit_names being > > valid. > > > > The LSM dump_common_audit_data() LSM_AUDIT_DATA_NET:AF_UNIX case was > > missed with the ghak96 patch, so add that case here. > > > > Thanks to bauen1 <j2468h(a)googlemail.com&gt; for reporting LSM situations in > > which context->cwd is not valid, inadvertantly fixed by the ghak96 patch. > > > > Please see upstream github issue > > https://github.com/linux-audit/audit-kernel/issues/120 > > This is also related to upstream github issue > > https://github.com/linux-audit/audit-kernel/issues/96 > > > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > --- > > Passes audit-testsuite. > > > > Chagelog: > > v4: > > - rebase on audit/next v5.9-rc1 > > - squash v2+v3fix > > - add pwd NULL check in audit_log_name() > > - resubmit after revert > > > > v3: > > - initialize fds[0] to -1 > > - init cwd for ghak96 LSM_AUDIT_DATA_NET:AF_UNIX case > > - init cwd for audit_inode{,_child} > > > > v2: > > - unconditionally clear dummy > > - create audit_clear_dummy accessor function > > - remove proctitle context and dummy checks > > > > kernel/audit.c | 1 + > > kernel/audit.h | 8 ++++++++ > > kernel/auditsc.c | 11 +++++++---- > > security/lsm_audit.c | 1 + > > 4 files changed, 17 insertions(+), 4 deletions(-) > > Comments below, but can you elaborate on if any testing was done > beyond the audit-testsuite? Yes, it was tested with audit-testsuite and bauen1's reproducer > > diff --git a/kernel/audit.h b/kernel/audit.h > > index 3b9c0945225a..abcfef58435b 100644 > > --- a/kernel/audit.h > > +++ b/kernel/audit.h > > @@ -290,6 +290,13 @@ extern int audit_signal_info_syscall(struct task_struct *t); > > extern void audit_filter_inodes(struct task_struct *tsk, > > struct audit_context *ctx); > > extern struct list_head *audit_killed_trees(void); > > + > > +static inline void audit_clear_dummy(struct audit_context *ctx) > > +{ > > + if (ctx) > > + ctx->dummy = 0; > > +} > > With the only caller being audit_log_start(), should this be moved to > kernel/audit.c? I'm just not sure this is something we would ever > need (or want) to call from elsewhere, thoughts? Yes, move it, or better yet just open code it.

> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > > index 8dba8f0983b5..9d2de93f40b3 100644 > > --- a/kernel/auditsc.c > > +++ b/kernel/auditsc.c > > @@ -1367,7 +1368,10 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n, > > /* name was specified as a relative path and the > > * directory component is the cwd > > */ > > - audit_log_d_path(ab, " name=", &context->pwd); > > + if (&context->pwd) > > Hmm, I don't think this is going to work the way you are intending; I > believe this will always evaluate to true regardless of the state of > context->pwd. If you look elsewhere in kernel/auditsc.c you will see > some examples of checking to see if context->pwd is valid (e.g. > _audit_getcwd() and audit_log_exit()). Sorry for the ctx->pwd.dentry/mnt brainfart, the compiler *did* complain.

> > + audit_log_d_path(ab, " name=", &context->pwd); > > + else > > + audit_log_format(ab, " name=(null)"); > > break; > > default: > > /* log the name's directory component */... > > > @@ -2079,6 +2080,7 @@ void __audit_inode(struct filename *name, const struct dentry *dentry, > > } > > handle_path(dentry); > > audit_copy_inode(n, dentry, inode, flags & AUDIT_INODE_NOEVAL); > > + _audit_getcwd(context); > > } > > > > void __audit_file(const struct file *file) > > @@ -2197,6 +2199,7 @@ void __audit_inode_child(struct inode *parent, > > audit_copy_inode(found_child, dentry, inode, 0); > > else > > found_child->ino = AUDIT_INO_UNSET; > > + _audit_getcwd(context); > > } > > EXPORT_SYMBOL_GPL(__audit_inode_child); > > > > diff --git a/security/lsm_audit.c b/security/lsm_audit.c > > index 53d0d183db8f..e93077612246 100644 > > --- a/security/lsm_audit.c > > +++ b/security/lsm_audit.c > > @@ -369,6 +369,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, > > audit_log_untrustedstring(ab, p); > > else > > audit_log_n_hex(ab, p, len); > > + audit_getcwd(); > > break; > > } > > } > > I'm starting to wonder if audit is doing this wrong (it is audit after > all) ... why not just fetch the cwd in audit_log_exit() if there are > entries in the context->names_list? The only time we care about > logging the working dir is when we actually have PATH records, right? > My initial thinking is that we can simplify a lot of code if we just > add a audit_getcwd() call in audit_log_exit() if the > context->names_list is not empty. We should even be safe in the task > exit case as the fs info appears to get cleaned up *after* > audit_log_exit() is called. > Assuming we go this route, we can probably get rid of all the > audit_getcwd() calls outside of the audit code (e.g. the lsm_audit.c > code). I guess we would need to make sure things still behave the > same for chdir(2), getcwd(2), etc. but even if we have to insert one > or two audit_getcwd() calls in that case we should still come out on > top (although I suspect the necessary calls are already being made). Or just open code audit_getcwd() in audit_alloc_name() and kill all audit_getcwd() calls since it is audit_names that is populated as the result of a call to audit_alloc_name(). How does this look?: 4 files changed, 9 insertions(+), 33 deletions(-)