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b=lURSPx/Kru0c7vLoWR3Kzj61JujCHkscmvvS8lo8D3qckJbFCHCsuwy2J5VXIb204 7Xea03siSIbW3VpXItIFMLe7+16Fg77Px00eUfc2u6iMC3zBZkeukLjMh/u+VyowpC ahQ+2U6iyd02SiN9ULBON4FVRj1QqoeknkEJKyQc6aIj78UMY/8DqZHw3ja1Pvkxfs TJEjsUJNil3Ag75JMPuNetiwm6lEZPO2dCd0iV28mMxXo6lLVCggsef+Xzig3pu0q2 28ixQZIHdQUWR5Ig2F8YCVlqjUNIxI4PiXzI4+ievr9xM+wFpvH4Vg3s3NAzkgg2g8 kITZ5aiZsglEg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v3 09/10] stackdepot: Store compressed frames in stack records Reply-To: sashiko-reviews@lists.linux.dev To: "Matt Fleming" , "Andrew Morton" , "Marco Elver" Cc: "Alexander Potapenko" , "Andrey Konovalov" , "Dmitry Vyukov" , "Oscar Salvador" , "Vlastimil Babka" , "Caleb Kan" , "Caleb Kan" , linux-mm@kvack.org, kasan-dev@googlegroups.com, kernel-team@cloudflare.com, "Matt Fleming" In-Reply-To: <20261113185702.1332171-10-matt@readmodwrite.com> References: <20261113185702.1332171-1-matt@readmodwrite.com> <20261113185702.1332171-10-matt@readmodwrite.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sat, 14 Nov 2026 18:58:07 +0000 X-Rspamd-Queue-Id: 17A42140002 X-Rspamd-Server: rspam12 X-Stat-Signature: a5343tpu551muwtnkzsg53mknbh5x34p X-Rspam-User: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794682689-755031 X-HE-Meta: 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 2qrEzCas 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue to consider: - [High] stackdepot: uninitialized frame in depot_stack_entry() on generic arches -- commit 8ef363f0fde887ad99497bbd2e7b00c5bd8bac35 Author: Matt Fleming stackdepot: Store compressed frames in stack records This commit stores stack frames in a 32-bit compressed array inside struct stack_record when all frames of a persistent stack trace can be compressed by architecture hooks. > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > index 8f1aaa0c6d889..f323f1e97e129 100644 > --- a/lib/stackdepot.c > +++ b/lib/stackdepot.c [ ... ] > @@ -419,9 +422,37 @@ static struct stack_record *depot_pop_free(void) > return stack; > } > =20 > -static inline size_t depot_stack_record_size(struct stack_record *s, uns= igned int nr_entries) > +/* Check whether every frame of a stack can be stored in 32 bits. */ > +static bool depot_entries_compressible(const unsigned long *entries, > + unsigned int nr_entries) > +{ > + u32 payload; > + > + for (unsigned int i =3D 0; i < nr_entries; i++) { > + if (!arch_stack_depot_frame_try_compress(entries[i], &payload)) > + return false; > + } > + return true; > +} > + > +static inline unsigned long depot_stack_entry(const struct stack_record = *stack, > + unsigned int i) > { > - const size_t used =3D flex_array_size(s, entries, nr_entries); > + unsigned long frame; > + > + if (!(stack->flags & STACK_RECORD_COMPRESSED)) > + return stack->entries[i]; > + arch_stack_depot_frame_decompress(stack->compressed_entries[i], &frame); > + return frame; > +} [Severity: High] Does depot_stack_entry() return an uninitialized frame on architectures using the generic header? include/asm-generic/stackdepot.h:arch_stack_depot_frame_decompress() { /* Generic code never compresses frames, so this hook is unreachable. */ } Because stack->flags is read at runtime and the generic arch_stack_depot_frame_decompress() neither writes to *frame nor calls unreachable(), the compiler cannot tell that the compressed branch is dead. In depot_stack_equal(), the early return when !(stack->flags & STACK_RECORD_COMPRESSED) folds the same check inside the inlined depot_stack_entry() call, leaving frame unconditionally uninitialized in the loop and triggering -Wuninitialized build failures under CONFIG_WERROR=3Dy. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261113185702.1332= 171-1-matt@readmodwrite.com?part=3D9