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Tue, 26 Nov 2024 08:33:39 -0800 (PST) Received: from eis ([2a04:ee41:4:b2de:1ac0:4dff:fe0f:3782]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5d01d3fcf86sm5261423a12.63.2024.11.26.08.33.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Nov 2024 08:33:38 -0800 (PST) Date: Tue, 26 Nov 2024 16:36:13 +0000 From: Anton Protopopov To: Alexei Starovoitov Cc: bpf , Jiri Olsa Subject: Re: [PATCH v2 bpf-next 5/6] bpf: fix potential error return Message-ID: References: <20241119101552.505650-1-aspsk@isovalent.com> <20241119101552.505650-6-aspsk@isovalent.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 24/11/25 05:43PM, Alexei Starovoitov wrote: > On Tue, Nov 19, 2024 at 2:17 AM Anton Protopopov wrote: > > > > The bpf_remove_insns() function returns WARN_ON_ONCE(error), where > > error is a result of bpf_adj_branches(), and thus should be always 0 > > However, if for any reason it is not 0, then it will be converted to > > boolean by WARN_ON_ONCE and returned to user space as 1, not an actual > > error value. Fix this by returning the original err after the WARN check. > > > > Signed-off-by: Anton Protopopov > > Acked-by: Jiri Olsa > > --- > > kernel/bpf/core.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > > index 14d9288441f2..a15059918768 100644 > > --- a/kernel/bpf/core.c > > +++ b/kernel/bpf/core.c > > @@ -539,6 +539,8 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, > > > > int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt) > > { > > + int err; > > + > > /* Branch offsets can't overflow when program is shrinking, no need > > * to call bpf_adj_branches(..., true) here > > */ > > @@ -546,7 +548,12 @@ int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt) > > sizeof(struct bpf_insn) * (prog->len - off - cnt)); > > prog->len -= cnt; > > > > - return WARN_ON_ONCE(bpf_adj_branches(prog, off, off + cnt, off, false)); > > + err = bpf_adj_branches(prog, off, off + cnt, off, false); > > + WARN_ON_ONCE(err); > > + if (err) > > + return err; > > + > > + return 0; > > That looks very odd. Just return err ? Ah, yes, thanks. This was supposed to be followed up by a patch which adds code in between, but as this patch is out of scope of this set, I will just return err here.