Re: [PATCH 3/3] audit: unify audit_filter_{uring(),inode_name(),syscall()}

On Tue, Sep 27, 2022 at 7:00 PM Ankur Arora <ankur.a.arora(a)oracle.com&gt; wrote: > > audit_filter_uring(), audit_filter_inode_name() are substantially similar > to audit_filter_syscall(). Move the core logic to __audit_filter() which > can be parametrized for all three. > > On a Skylakex system, getpid() latency (all results aggregated > across 12 boot cycles): > > Min Mean Median Max pstdev > (ns) (ns) (ns) (ns) > > - 173.11 182.51 179.65 202.09 (+- 4.34%) > + 162.11 175.26 173.71 190.56 (+- 4.33%) > > Performance counter stats for 'bin/getpid' (3 runs) go from: > cycles 706.13 ( +- 4.13% ) > instructions 1654.70 ( +- .06% ) > IPC 2.35 ( +- 4.25% ) > branches 430.99 ( +- .06% ) > branch-misses 0.50 ( +- 2.00% ) > L1-dcache-loads 440.02 ( +- .07% ) > L1-dcache-load-misses 5.22 ( +- 82.75% ) > > to: > cycles 678.79 ( +- 4.22% ) > instructions 1657.79 ( +- .05% ) > IPC 2.45 ( +- 4.08% ) > branches 432.00 ( +- .05% ) > branch-misses 0.38 ( +- 23.68% ) > L1-dcache-loads 444.96 ( +- .03% ) > L1-dcache-load-misses 5.13 ( +- 73.09% ) > > (Both aggregated over 12 boot cycles.) > > Unclear if the improvement is just run-to-run variation or because of > a slightly denser loop (the list parameter in the list_for_each_entry_rcu() > exit check now comes from a register rather than a constant as before.) > > Signed-off-by: Ankur Arora <ankur.a.arora(a)oracle.com&gt; > --- > kernel/auditsc.c | 86 +++++++++++++++++++++++++----------------------- > 1 file changed, 44 insertions(+), 42 deletions(-) > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > index bf26f47b5226..dd89a52988b0 100644 > --- a/kernel/auditsc.c > +++ b/kernel/auditsc.c > @@ -805,6 +805,41 @@ static bool audit_in_mask(const struct audit_krule *rule, unsigned long val) > return rule->mask[word] & bit; > } > > +/** > + * __audit_filter - common filter > + * Please remove the vertical whitespace between the function description line and the parameter descriptions. I'd also suggest renaming this function to "__audit_filter_op(...)" since we have a few audit filtering functions and a generic "__audit_filter()" function with no qualification in the name seems just a bit too generic to not be misleading ... at least I think so. I also might try to be just a bit more descriptive in the text above, for example: "__audit_filter_op - filter helper function for operations (syscall/uring/etc.)" > + * @tsk: associated task > + * @ctx: audit context > + * @list: audit filter list > + * @op: current syscall/uring_op > + * @name: name to be filtered (used by audit_filter_inode_name) I would change this to "@name: audit_name to use in filtering (can be NULL)" and leave it at that. > + * > + * return: 1 if we hit a filter, 0 if we don't The function header block comment description should be in regular English sentences. Perhaps something like this: "Run the audit filters specified in @list against @tsk using @ctx, @op, and @name as necessary; the caller is responsible for ensuring that the call is made while the RCU read lock is held. The @name parameter can be NULL, but all others must be specified. Returns 1/true if the filter finds a match, 0/false if none are found." > + */ > +static int __audit_filter(struct task_struct *tsk, > + struct audit_context *ctx, > + struct list_head *list, > + unsigned long op, > + struct audit_names *name) > +{ > + struct audit_entry *e; > + enum audit_state state; > + > + rcu_read_lock(); I would move the RCU locking to the callers since not every caller requires it. > + list_for_each_entry_rcu(e, list, list) { > + if (unlikely(audit_in_mask(&e->rule, op))) { As discussed in patch 2/3, please remove the unlikely() call.

> + if (audit_filter_rules(tsk, &e->rule, ctx, name, > + &state, false)) { > + rcu_read_unlock(); > + ctx->current_state = state; > + return 1; > + } > + } > + } > + rcu_read_unlock(); > + return 0; > +} > +