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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id u20sm1917349pfm.152.2020.06.24.00.20.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 00:20:58 -0700 (PDT) Date: Wed, 24 Jun 2020 00:20:57 -0700 From: Kees Cook To: Kristen Carlson Accardi Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Tony Luck Subject: Re: [PATCH v3 09/10] kallsyms: Hide layout Message-ID: <202006240013.7806A28435@keescook> References: <20200623172327.5701-1-kristen@linux.intel.com> <20200623172327.5701-10-kristen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200623172327.5701-10-kristen@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 23, 2020 at 10:23:26AM -0700, Kristen Carlson Accardi wrote: > This patch makes /proc/kallsyms display alphabetically by symbol > name rather than sorted by address in order to hide the newly > randomized address layout. > > Signed-off-by: Kristen Carlson Accardi > Reviewed-by: Tony Luck > Tested-by: Tony Luck > --- > kernel/kallsyms.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 128 insertions(+) > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index 16c8c605f4b0..df2b20e1b7f2 100644 > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -25,6 +25,7 @@ > #include > #include > #include > +#include > > /* > * These will be re-linked against their real values > @@ -446,6 +447,11 @@ struct kallsym_iter { > int show_value; > }; > > +struct kallsyms_iter_list { > + struct kallsym_iter iter; > + struct list_head next; > +}; > + > int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, > char *type, char *name) > { > @@ -660,6 +666,127 @@ int kallsyms_show_value(void) > } > } The #ifdef can be moved up to here: #ifdef CONFIG_FG_KASLR Otherwise without CONFIG_FG_KASLR, I get: kernel/kallsyms.c:714:12: warning: ‘kallsyms_list_cmp’ defined but not used [-Wunused-function] 714 | static int kallsyms_list_cmp(void *priv, struct list_head *a, | ^~~~~~~~~~~~~~~~~ > > +static int sorted_show(struct seq_file *m, void *p) > +{ > + struct list_head *list = m->private; > + struct kallsyms_iter_list *iter; > + int rc; > + > + if (list_empty(list)) > + return 0; > + > + iter = list_first_entry(list, struct kallsyms_iter_list, next); > + > + m->private = iter; > + rc = s_show(m, p); > + m->private = list; > + > + list_del(&iter->next); > + kfree(iter); > + > + return rc; > +} > + > +static void *sorted_start(struct seq_file *m, loff_t *pos) > +{ > + return m->private; > +} > + > +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos) > +{ > + struct list_head *list = m->private; > + > + (*pos)++; > + > + if (list_empty(list)) > + return NULL; > + > + return p; > +} > + > +static const struct seq_operations kallsyms_sorted_op = { > + .start = sorted_start, > + .next = sorted_next, > + .stop = s_stop, > + .show = sorted_show > +}; > + > +static int kallsyms_list_cmp(void *priv, struct list_head *a, > + struct list_head *b) > +{ > + struct kallsyms_iter_list *iter_a, *iter_b; > + > + iter_a = list_entry(a, struct kallsyms_iter_list, next); > + iter_b = list_entry(b, struct kallsyms_iter_list, next); > + > + return strcmp(iter_a->iter.name, iter_b->iter.name); > +} > + > +int get_all_symbol_name(void *data, const char *name, struct module *mod, > + unsigned long addr) This can be static too. Otherwise, looks good! Reviewed-by: Kees Cook -- Kees Cook