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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id uz16-20020a170907119000b00a3d2ccea999sm1601095ejb.35.2024.02.16.06.27.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Feb 2024 06:27:45 -0800 (PST) Message-ID: <9e19786565a3fbfea58dcd25bba644fe8e0ed6b0.camel@gmail.com> Subject: Re: [PATCH bpf-next 2/3] bpf: check bpf_func_state->callback_depth when pruning states From: Eduard Zingerman To: Yonghong Song , bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, kuniyu@amazon.com Date: Fri, 16 Feb 2024 16:27:44 +0200 In-Reply-To: <1fbcd9f1-6c83-4430-b797-a92285d1d151@linux.dev> References: <20240212143832.28838-1-eddyz87@gmail.com> <20240212143832.28838-3-eddyz87@gmail.com> <925915504557d991bf9b576a362e0ef4a8953795.camel@gmail.com> <0e5b990eeaa63590e067c8ac10642b6bc6d0e9a8.camel@gmail.com> <1fbcd9f1-6c83-4430-b797-a92285d1d151@linux.dev> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2024-02-14 at 09:42 -0800, Yonghong Song wrote: > > .------------------------------------- Checkpoint / State name > > | .-------------------------------- Code point number > > | | .---------------------------- Stack state {ctx.a,ctx.b,ctx.c= } > > | | | .------------------- Callback depth in frame #0 > > v v v v > > 1 - (0) {7P,7P,7},depth=3D0 > > 2 - (3) {7P,7P,7},depth=3D1 > > 3 - (0) {7P,7P,42},depth=3D1 > > (a) - (3) {7P,7,42},depth=3D2 > > 4 - (0) {7P,7,42},depth=3D2 loop terminates because of de= pth limit > > 5 - (4) {7P,7,42},depth=3D0 predicted false, ctx.a marked= precise > > 6 - (6) exit > > 7 - (2) {7P,7,42},depth=3D2 > > 8 - (0) {7P,42,42},depth=3D2 loop terminates because of de= pth limit > > 9 - (4) {7P,42,42},depth=3D0 predicted false, ctx.a marked= precise > > 10 - (6) exit > > (b) - (1) {7P,7P,42},depth=3D2 > > 11 - (0) {42P,7P,42},depth=3D2 loop terminates because of de= pth limit > > 12 - (4) {42P,7P,42},depth=3D0 predicted false, ctx.{a,b} ma= rked precise > > 13 - (6) exit > > 14 - (2) {7P,7,7},depth=3D1 > > 15 - (0) {7P,42,7},depth=3D1 considered safe, pruned using= checkpoint (a) > > (c) - (1) {7P,7P,7},depth=3D1 considered safe, pruned using= checkpoint (b) >=20 > For the above line > (c) - (1) {7P,7P,7},depth=3D1 considered safe, pruned usi= ng checkpoint (b) > I would change to > (c) - (1) {7P,7P,7},depth=3D1 > - (0) {42P, 7P, 7},depth =3D 1 considered safe, pruned usi= ng checkpoint (11) At that point: - there is a checkpoint at (1) with state {7P,7P,42} - verifier is at (1) in state {7,7,7} Thus, verifier won't proceed to (0) because {7,7,7} is states_equal to {7P,= 7P,42}. > For > 14 - (2) {7P,7,7},depth=3D1 > 15 - (0) {7P,42,7},depth=3D1 considered safe, pruned using c= heckpoint (a) > I suspect for line 15, the pruning uses checking point at line (8). Right, because checkpoints for a particular insn form a stack. My bad. > Other than the above, the diagram LGTM. Thank you for the feedback, I'll post v2 shortly.