From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Joel Fernandes (Google)" Subject: [PATCH v2 1/3] module: Prepare for addition of new ro_after_init sections Date: Wed, 10 Apr 2019 15:08:21 -0400 Message-Id: <20190410190823.109172-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , paulmck@linux.vnet.ibm.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, rcu@vger.kernel.org, kernel-hardening@lists.openwall.com, kernel-team@android.com, keescook@chromium.org, Jessica Yu List-ID: For the purposes of hardening modules by adding sections to ro_after_init sections, prepare for addition of new ro_after_init entries which we do in future patches. Create a table to which new entries could be added later. This makes it less error prone and reduce code duplication. Cc: paulmck@linux.vnet.ibm.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: rcu@vger.kernel.org Cc: kernel-hardening@lists.openwall.com Cc: kernel-team@android.com Suggested-by: keescook@chromium.org Reviewed-by: keescook@chromium.org Acked-by: rostedt@goodmis.org Signed-off-by: Joel Fernandes (Google) --- kernel/module.c | 41 +++++++++++++++++++++++------------------ 1 file changed, 23 insertions(+), 18 deletions(-) diff --git a/kernel/module.c b/kernel/module.c index 524da609c884..1acddb93282a 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3300,11 +3300,27 @@ static bool blacklisted(const char *module_name) } core_param(module_blacklist, module_blacklist, charp, 0400); +/* + * Mark ro_after_init section with SHF_RO_AFTER_INIT so that + * layout_sections() can put it in the right place. + * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set. + */ +static char *ro_after_init_sections[] = { + ".data..ro_after_init", + + /* + * __jump_table structures are never modified, with the exception of + * entries that refer to code in the __init section, which are + * annotated as such at module load time. + */ + "__jump_table", +}; + static struct module *layout_and_allocate(struct load_info *info, int flags) { struct module *mod; unsigned int ndx; - int err; + int err, i; err = check_modinfo(info->mod, info, flags); if (err) @@ -3319,23 +3335,12 @@ static struct module *layout_and_allocate(struct load_info *info, int flags) /* We will do a special allocation for per-cpu sections later. */ info->sechdrs[info->index.pcpu].sh_flags &= ~(unsigned long)SHF_ALLOC; - /* - * Mark ro_after_init section with SHF_RO_AFTER_INIT so that - * layout_sections() can put it in the right place. - * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set. - */ - ndx = find_sec(info, ".data..ro_after_init"); - if (ndx) - info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT; - /* - * Mark the __jump_table section as ro_after_init as well: these data - * structures are never modified, with the exception of entries that - * refer to code in the __init section, which are annotated as such - * at module load time. - */ - ndx = find_sec(info, "__jump_table"); - if (ndx) - info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT; + /* Set sh_flags for read-only after init sections */ + for (i = 0; ro_after_init_sections[i]; i++) { + ndx = find_sec(info, ro_after_init_sections[i]); + if (ndx) + info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT; + } /* Determine total sizes, and put offsets in sh_entsize. For now this is done generically; there doesn't appear to be any -- 2.21.0.392.gf8f6787159e-goog