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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id l11sm2222672pjy.44.2020.03.26.13.34.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 13:34:09 -0700 (PDT) Date: Thu, 26 Mar 2020 13:34:08 -0700 From: Kees Cook To: Vlastimil Babka Cc: Luis Chamberlain , Iurii Zaikin , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org, Ivan Teterevkov , Michal Hocko , David Rientjes , Matthew Wilcox , "Eric W . Biederman" , "Guilherme G . Piccoli" Subject: Re: [RFC v3 2/2] kernel/sysctl: support handling command line aliases Message-ID: <202003261329.AAFEE9C@keescook> References: <20200326181606.7027-1-vbabka@suse.cz> <20200326181606.7027-2-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200326181606.7027-2-vbabka@suse.cz> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 26, 2020 at 07:16:06PM +0100, Vlastimil Babka wrote: > We can now handle sysctl parameters on kernel command line, but historically > some parameters introduced their own command line equivalent, which we don't > want to remove for compatibility reasons. We can however convert them to the > generic infrastructure with a table translating the legacy command line > parameters to their sysctl names, and removing the one-off param handlers. > > This patch adds the support and makes the first conversion to demonstrate it, > on the (deprecated) numa_zonelist_order parameter. > > Signed-off-by: Vlastimil Babka > --- > Changes in v3: > - constify some things according to Kees > - expand the comment of sysctl_aliases to note on different timings > > fs/proc/proc_sysctl.c | 48 ++++++++++++++++++++++++++++++++++++------- > mm/page_alloc.c | 9 -------- > 2 files changed, 41 insertions(+), 16 deletions(-) > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c > index 8ee3273e4540..3a861e0a7c7e 100644 > --- a/fs/proc/proc_sysctl.c > +++ b/fs/proc/proc_sysctl.c > @@ -1729,6 +1729,37 @@ int __init proc_sys_init(void) > > struct vfsmount *proc_mnt = NULL; > > +struct sysctl_alias { > + const char *kernel_param; > + const char *sysctl_param; > +}; > + > +/* > + * Historically some settings had both sysctl and a command line parameter. > + * With the generic sysctl. parameter support, we can handle them at a single > + * place and only keep the historical name for compatibility. This is not meant > + * to add brand new aliases. When adding existing aliases, consider whether > + * the possibly different moment of changing the value (e.g. from early_param > + * to the moment do_sysctl_args() is called) is an issue for the specific > + * parameter. > + */ > +static const struct sysctl_alias sysctl_aliases[] = { > + {"numa_zonelist_order", "vm.numa_zonelist_order" }, > + { } > +}; > + > +const char *sysctl_find_alias(char *param) This should be "static" too. > +{ > + const struct sysctl_alias *alias; > + > + for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) { > + if (strcmp(alias->kernel_param, param) == 0) > + return alias->sysctl_param; > + } > + > + return NULL; > +} > + > /* Set sysctl value passed on kernel command line. */ > static int process_sysctl_arg(char *param, char *val, > const char *unused, void *arg) > @@ -1741,15 +1772,18 @@ static int process_sysctl_arg(char *param, char *val, > loff_t pos = 0; > ssize_t wret; > > - if (strncmp(param, "sysctl", sizeof("sysctl") - 1)) > - return 0; > - > - param += sizeof("sysctl") - 1; > + if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) { > + param += sizeof("sysctl") - 1; > > - if (param[0] != '/' && param[0] != '.') > - return 0; > + if (param[0] != '/' && param[0] != '.') > + return 0; > > - param++; > + param++; > + } else { > + param = (char *) sysctl_find_alias(param); > + if (!param) > + return 0; > + } > > if (!proc_mnt) { > proc_fs_type = get_fs_type("proc"); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3c4eb750a199..de7a134b1b8a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5460,15 +5460,6 @@ static int __parse_numa_zonelist_order(char *s) > return 0; > } > > -static __init int setup_numa_zonelist_order(char *s) > -{ > - if (!s) > - return 0; > - > - return __parse_numa_zonelist_order(s); > -} > -early_param("numa_zonelist_order", setup_numa_zonelist_order); > - > char numa_zonelist_order[] = "Node"; > > /* > -- > 2.25.1 > Otherwise, yay, I love it! :) -- Kees Cook