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Fri, 07 Nov 2025 05:14:59 -0800 (PST) Date: Fri, 7 Nov 2025 14:14:57 +0100 From: Petr Mladek To: bot+bpf-ci@kernel.org Cc: petr.pavlu@suse.com, rostedt@goodmis.org, ast@kernel.org, akpm@linux-foundation.org, kees@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, mhiramat@kernel.org, mark.rutland@arm.com, mcgrof@kernel.org, da.gomez@kernel.org, samitolvanen@google.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-modules@vger.kernel.org, linux-trace-kernel@vger.kernel.org, andrii@kernel.org, martin.lau@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [PATCH 2/6] kallsyms: Cleanup code for appending the module buildid Message-ID: References: <20251105142319.1139183-3-pmladek@suse.com> <451acb410ee1ce42f7fb2da9f3b8162708f40788cb849cc0f50851ad16813349@mail.kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <451acb410ee1ce42f7fb2da9f3b8162708f40788cb849cc0f50851ad16813349@mail.kernel.org> On Wed 2025-11-05 14:59:53, bot+bpf-ci@kernel.org wrote: > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > > index 1e7635864..9455e3bb0 100644 > > --- a/kernel/kallsyms.c > > +++ b/kernel/kallsyms.c > > @@ -423,6 +423,37 @@ int lookup_symbol_name(unsigned long addr, char *symname) > > return lookup_module_symbol_name(addr, symname); > > } > > > > +#ifdef CONFIG_STACKTRACE_BUILD_ID > > + > > +static int append_buildid(char *buffer, const char *modname, > > + const unsigned char *buildid) > > +{ > > + if (!modname) > > + return 0; > > + > > + if (!buildid) { > > + pr_warn_once("Undefined buildid for the module %s\n", modname); > > + return 0; > > + } > > When ftrace_mod_address_lookup() succeeds in kallsyms_lookup_buildid(), > it sets *modname but doesn't initialize *modbuildid. This leaves the > buildid variable uninitialized when __sprint_symbol() calls > append_buildid(). Just for record. This is a great analyze. This patchset is fixing this bug in a later patch. ;-) > Can the check above read uninitialized memory?> > Looking at kallsyms_lookup_buildid(): > - module_address_lookup() properly initializes both modname and > modbuildid > - bpf_address_lookup() sets modname=NULL (so append_buildid isn't > called) > - ftrace_mod_address_lookup() sets modname=mod_map->mod->name but has > no modbuildid parameter > > The commit message mentions wanting to catch when lookup functions don't > handle buildid, but shouldn't kallsyms_lookup_buildid() initialize > *modbuildid=NULL before calling the lookup functions to avoid undefined > behavior? It seems that we are going this way, see https://lore.kernel.org/all/aQ3vWIqG31BgE4YD@pathway.suse.cz/ Best Regards, Petr