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Hermes SMTP Server) with ESMTPA ID b10af0932dc8e225430908a16a0d3a50; Thu, 22 May 2025 21:26:24 +0000 (UTC) Message-ID: <8bb003b3-8026-462c-ae9e-fd79fdb47ad5@schaufler-ca.com> Date: Thu, 22 May 2025 14:26:22 -0700 Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 08/29] lsm: get rid of the lsm_names list and do some cleanup To: Paul Moore , linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org Cc: John Johansen , Mimi Zohar , Roberto Sassu , Fan Wu , =?UTF-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , =?UTF-8?Q?G=C3=BCnther_Noack?= , Kees Cook , Micah Morton , Tetsuo Handa , Casey Schaufler References: <20250409185019.238841-31-paul@paul-moore.com> <20250409185019.238841-39-paul@paul-moore.com> Content-Language: en-US From: Casey Schaufler In-Reply-To: <20250409185019.238841-39-paul@paul-moore.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Mailer: WebService/1.1.23884 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo On 4/9/2025 11:49 AM, Paul Moore wrote: > The LSM currently has a lot of code to maintain a list of the > currently active LSMs in a human readable string, with the only > user being the "/sys/kernel/security/lsm" code. Let's drop all > of that code and generate the string on an as-needed basis when > userspace reads "/sys/kernel/security/lsm". > > Signed-off-by: Paul Moore > --- > include/linux/lsm_hooks.h | 1 - > security/inode.c | 27 +++++++++++++++++++-- > security/lsm_init.c | 49 --------------------------------------- > 3 files changed, 25 insertions(+), 52 deletions(-) > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index 4cd17c9a229f..bc477fb20d02 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -169,7 +169,6 @@ struct lsm_info { > > > /* DO NOT tamper with these variables outside of the LSM framework */ > -extern char *lsm_names; > extern struct lsm_static_calls_table static_calls_table __ro_after_init; > > /** > diff --git a/security/inode.c b/security/inode.c > index da3ab44c8e57..49bc3578bd23 100644 > --- a/security/inode.c > +++ b/security/inode.c > @@ -22,6 +22,8 @@ > #include > #include > > +#include "lsm.h" > + > static struct vfsmount *mount; > static int mount_count; > > @@ -343,8 +345,29 @@ static struct dentry *lsm_dentry; > static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count, > loff_t *ppos) > { > - return simple_read_from_buffer(buf, count, ppos, lsm_names, > - strlen(lsm_names)); > + int i; > + char *str; > + ssize_t rc, len = 0; > + > + for (i = 0; i < lsm_count; i++) > + /* the '+ 1' accounts for either a comma or a NUL terminator */ > + len += strlen(lsm_order[i]->id->name) + 1; > + > + str = kmalloc(len, GFP_KERNEL); > + if (!str) > + return -ENOMEM; > + str[0] = '\0'; > + > + i = 0; > + while (i < lsm_count) { > + strcat(str, lsm_order[i]->id->name); > + if (++i < lsm_count) > + strcat(str, ","); > + } > + > + rc = simple_read_from_buffer(buf, count, ppos, str, len); This results in a trailing nul byte at the end of the string. > + kfree(str); > + return rc; > } > > static const struct file_operations lsm_ops = { > diff --git a/security/lsm_init.c b/security/lsm_init.c > index 981ddb20f48e..978bb81b58fa 100644 > --- a/security/lsm_init.c > +++ b/security/lsm_init.c > @@ -10,8 +10,6 @@ > > #include "lsm.h" > > -char *lsm_names; > - > /* Pointers to LSM sections defined in include/asm-generic/vmlinux.lds.h */ > extern struct lsm_info __start_lsm_info[], __end_lsm_info[]; > extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; > @@ -363,42 +361,6 @@ static void __init lsm_init_ordered(void) > } > } > > -static bool match_last_lsm(const char *list, const char *lsm) > -{ > - const char *last; > - > - if (WARN_ON(!list || !lsm)) > - return false; > - last = strrchr(list, ','); > - if (last) > - /* Pass the comma, strcmp() will check for '\0' */ > - last++; > - else > - last = list; > - return !strcmp(last, lsm); > -} > - > -static int lsm_append(const char *new, char **result) > -{ > - char *cp; > - > - if (*result == NULL) { > - *result = kstrdup(new, GFP_KERNEL); > - if (*result == NULL) > - return -ENOMEM; > - } else { > - /* Check if it is the last registered name */ > - if (match_last_lsm(*result, new)) > - return 0; > - cp = kasprintf(GFP_KERNEL, "%s,%s", *result, new); > - if (cp == NULL) > - return -ENOMEM; > - kfree(*result); > - *result = cp; > - } > - return 0; > -} > - > static void __init lsm_static_call_init(struct security_hook_list *hl) > { > struct lsm_static_call *scall = hl->scalls; > @@ -435,15 +397,6 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count, > hooks[i].lsmid = lsmid; > lsm_static_call_init(&hooks[i]); > } > - > - /* > - * Don't try to append during early_security_init(), we'll come back > - * and fix this up afterwards. > - */ > - if (slab_is_available()) { > - if (lsm_append(lsmid->name, &lsm_names) < 0) > - panic("%s - Cannot get early memory.\n", __func__); > - } > } > > int __init early_security_init(void) > @@ -480,8 +433,6 @@ int __init security_init(void) > lsm_early_for_each_raw(lsm) { > init_debug(" early started: %s (%s)\n", lsm->id->name, > is_enabled(lsm) ? "enabled" : "disabled"); > - if (lsm->enabled) > - lsm_append(lsm->id->name, &lsm_names); > } > > /* Load LSMs in specified order. */