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s=20210705; t=1744756214; bh=7xg0mN2qYJiYxvFo4La6OGn/H9iXblVBNB/eOGi69YQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AA2M7U8E61gLuAtcR1MmlnIHrroDzdhpethO12wDheKLYEsDn0BFZSvvz2hUv3JU1 dNTLPQ45deS9jLcH/7ILfj3kFgsZiwUByT99Fqn3XIT/3jn+BOQxBo9bH2AS1cP8f9 E4N70yHqlo1RTGSkzl0JzaM7IheoVcsxIktE0/Fsy4/dHlVF5xuUZYAvIxrwQI6oee GOfcMioubIue8gJ38yfqGGN3ahvz71Sxk1LFHTmrdtVXW+EjXwdMpJ+LvxEK/IL5V6 2QimebIE0KeFYdqEUKNvKqUSAjhbmFxzse9PNoe5F256NSZQSOu4Hdg2t5AY+msBXJ ju7raYw6ODygA== Message-ID: <03eeafb2-12e7-44a2-b0fc-cf26fa256f1b@canonical.com> Date: Tue, 15 Apr 2025 15:30:10 -0700 Precedence: bulk X-Mailing-List: linux-security-module@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 , Kees Cook Cc: linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, Mimi Zohar , Roberto Sassu , Fan Wu , =?UTF-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , =?UTF-8?Q?G=C3=BCnther_Noack?= , Micah Morton , Casey Schaufler , Tetsuo Handa References: <20250409185019.238841-31-paul@paul-moore.com> <20250409185019.238841-39-paul@paul-moore.com> <202504091607.0A394D5EF@keescook> Content-Language: en-US From: John Johansen Autocrypt: addr=john.johansen@canonical.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 4/10/25 15:47, Paul Moore wrote: > On Wed, Apr 9, 2025 at 7:13 PM Kees Cook wrote: >> >> On Wed, Apr 09, 2025 at 02:49:53PM -0400, 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(-) > > ... > >>> @@ -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); >>> + kfree(str); >>> + return rc; >> >> Hrm, at least cache it? > > Are you aware of a performance critical use of this? > no I can't see anything performance critical, I think it just is cleaner to only generate once if after init the list doesn't change. >> Better yet, do this whole thing in a initcall after LSMs are loaded, and >> both can gain __ro_after_init... > > I *really* disliked all the stuff we were having to do during boot, > and all the redundant global state we were keeping around. I'll go > ahead and cache the lsm_read() result local to the function but that's > probably all I'm going to accept at this point in time. > fair, I don't even think this needs to be changed, I think kees's suggestion is more of a nice to have