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Thu, 22 Dec 2022 15:20:17 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 23 Dec 2022 00:20:15 +0100 To: Paul Moore Subject: Re: [PATCH] bpf: restore the ebpf audit UNLOAD id field Message-ID: References: <20221222001343.489117-1-paul@paul-moore.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Mailman-Approved-At: Fri, 23 Dec 2022 14:08:28 +0000 X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: bpf@vger.kernel.org, linux-audit@redhat.com, Burn Alting , sdf@google.com, Alexei Starovoitov Errors-To: linux-audit-bounces@redhat.com Sender: "Linux-audit" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, Dec 22, 2022 at 02:03:41PM -0500, Paul Moore wrote: > On Thu, Dec 22, 2022 at 12:19 PM wrote: > > On 12/21, Paul Moore wrote: > > > When changing the ebpf program put() routines to support being called > > > from within IRQ context the program ID was reset to zero prior to > > > generating the audit UNLOAD record, which obviously rendered the ID > > > field bogus (always zero). This patch resolves this by adding a new > > > field, bpf_prog_aux::id_audit, which is set when the ebpf program is > > > allocated an ID and never reset, ensuring a valid ID field, > > > regardless of the state of the original ID field, bpf_prox_aud::id. > > > > > I also modified the bpf_audit_prog() logic used to associate the > > > AUDIT_BPF record with other associated records, e.g. @ctx != NULL. > > > Instead of keying off the operation, it now keys off the execution > > > context, e.g. '!in_irg && !irqs_disabled()', which is much more > > > appropriate and should help better connect the UNLOAD operations with > > > the associated audit state (other audit records). > > > > [..] > > > > > As an note to future bug hunters, I did briefly consider removing the > > > ID reset in bpf_prog_free_id(), as it would seem that once the > > > program is removed from the idr pool it can no longer be found by its > > > ID value, but commit ad8ad79f4f60 ("bpf: offload: free program id > > > when device disappears") seems to imply that it is beneficial to > > > reset the ID value. Perhaps as a secondary indicator that the ebpf > > > program is unbound/orphaned. > > > > That seems like the way to go imho. Can we have some extra 'invalid_id' > > bitfield in the bpf_prog so we can set it in bpf_prog_free_id and > > check in bpf_prog_free_id (for this offloaded use-case)? Because > > having two ids and then keeping track about which one to use, depending > > on the context, seems more fragile? > > I would definitely prefer to keep just a single ID value, and that was > the first approach I took when drafting this patch, but when looking > through the git log it looked like there was some desire to reset the > ID to zero on free. Not being an expert on the ebpf kernel code I > figured I would just write the patch up this way and make a comment > about not zero'ing out the ID in the commit description so we could > have a discussion about it. > > I'm not seeing any other comments, so I'll go ahead with putting > together a v2 that sets an invalid flag/bit and I'll post that for > further discussion/review. great, perf suffers the same issue: https://lore.kernel.org/bpf/Y3SRWVoycV290S16@krava/ any chance you could include it as well? I can send a patch later if needed thanks, jirka > > > > Fixes: d809e134be7a ("bpf: Prepare bpf_prog_put() to be called from irq > > > context.") > > > Reported-by: Burn Alting > > > Signed-off-by: Paul Moore > > > --- > > > include/linux/bpf.h | 1 + > > > kernel/bpf/syscall.c | 8 +++++--- > > > 2 files changed, 6 insertions(+), 3 deletions(-) > > -- > paul-moore.com -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit