* [PATCH] init/do_mounts.c: replace sys_mount() to do_mount() @ 2010-08-17 12:37 Namhyung Kim 2010-08-17 13:15 ` Arnd Bergmann 0 siblings, 1 reply; 5+ messages in thread From: Namhyung Kim @ 2010-08-17 12:37 UTC (permalink / raw) To: Ingo Molnar, Andrew Morton; +Cc: Alexander Viro, linux-kernel sys_mount() just copies all (string) arguments from user space to kernel and calls do_mount(). In this case we have all args in kernel already so there is no need to call sys_mount(). One thing we should take care is 'data' have to be in a page unless it is NULL. Do it manually. Signed-off-by: Namhyung Kim <namhyung@gmail.com> --- init/do_mounts.c | 18 ++++++++++++++++-- 1 files changed, 16 insertions(+), 2 deletions(-) diff --git a/init/do_mounts.c b/init/do_mounts.c index 02e3ca4..8eabff6 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -217,7 +217,21 @@ static void __init get_fs_names(char *page) static int __init do_mount_root(char *name, char *fs, int flags, void *data) { - int err = sys_mount(name, "/root", fs, flags, data); + int err; + unsigned long data_page = 0; + + if (data) { + /* data should be in a page */ + data_page = __get_free_page(GFP_KERNEL); + if (!data_page) + return -ENOMEM; + strlcpy((char *) data_page, data, PAGE_SIZE); + } + + err = do_mount(name, "/root", fs, flags, (void *) data_page); + + if (data_page) + free_page(data_page); if (err) return err; @@ -417,6 +431,6 @@ void __init prepare_namespace(void) mount_root(); out: devtmpfs_mount("dev"); - sys_mount(".", "/", NULL, MS_MOVE, NULL); + do_mount(".", "/", NULL, MS_MOVE, NULL); sys_chroot("."); } -- 1.7.0.4 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] init/do_mounts.c: replace sys_mount() to do_mount() 2010-08-17 12:37 [PATCH] init/do_mounts.c: replace sys_mount() to do_mount() Namhyung Kim @ 2010-08-17 13:15 ` Arnd Bergmann 2010-08-17 13:25 ` Namhyung Kim 0 siblings, 1 reply; 5+ messages in thread From: Arnd Bergmann @ 2010-08-17 13:15 UTC (permalink / raw) To: Namhyung Kim; +Cc: Ingo Molnar, Andrew Morton, Alexander Viro, linux-kernel On Tuesday 17 August 2010, Namhyung Kim wrote: > static int __init do_mount_root(char *name, char *fs, int flags, void *data) > { > - int err = sys_mount(name, "/root", fs, flags, data); > + int err; > + unsigned long data_page = 0; > + > + if (data) { > + /* data should be in a page */ > + data_page = __get_free_page(GFP_KERNEL); > + if (!data_page) > + return -ENOMEM; > + strlcpy((char *) data_page, data, PAGE_SIZE); > + } > + > + err = do_mount(name, "/root", fs, flags, (void *) data_page); > + > + if (data_page) > + free_page(data_page); AFAICT there is no need for the copy at all here. The reason that sys_mount copies to a separate page is that it gets passed an arbitrary-length user input. Arnd ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] init/do_mounts.c: replace sys_mount() to do_mount() 2010-08-17 13:15 ` Arnd Bergmann @ 2010-08-17 13:25 ` Namhyung Kim 2010-08-17 13:41 ` Arnd Bergmann 0 siblings, 1 reply; 5+ messages in thread From: Namhyung Kim @ 2010-08-17 13:25 UTC (permalink / raw) To: Arnd Bergmann; +Cc: Ingo Molnar, Andrew Morton, Alexander Viro, linux-kernel 2010-08-17 (화), 15:15 +0200, Arnd Bergmann: > AFAICT there is no need for the copy at all here. The reason that sys_mount > copies to a separate page is that it gets passed an arbitrary-length user > input. > > Arnd Right. But make sure to user options never exceed a page, do_mount() has following code: if (data_page) ((char *)data_page)[PAGE_SIZE - 1] = 0; -- Regards, Namhyung Kim ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] init/do_mounts.c: replace sys_mount() to do_mount() 2010-08-17 13:25 ` Namhyung Kim @ 2010-08-17 13:41 ` Arnd Bergmann 2010-08-17 14:38 ` [PATCH v2] init: " Namhyung Kim 0 siblings, 1 reply; 5+ messages in thread From: Arnd Bergmann @ 2010-08-17 13:41 UTC (permalink / raw) To: Namhyung Kim; +Cc: Ingo Molnar, Andrew Morton, Alexander Viro, linux-kernel On Tuesday 17 August 2010, Namhyung Kim wrote: > 2010-08-17 (화), 15:15 +0200, Arnd Bergmann: > > AFAICT there is no need for the copy at all here. The reason that sys_mount > > copies to a separate page is that it gets passed an arbitrary-length user > > input. > > Right. But make sure to user options never exceed a page, do_mount() has > following code: > > if (data_page) > ((char *)data_page)[PAGE_SIZE - 1] = 0; Hmm, how very unexpected... Maybe you can fix that as well in the same patch and move this safeguard into the copy_mount_options() function? I guess ideally we'd even mark the arguments to do_mount() as pointers to const, but that might create an excessive amount of churn. Arnd ^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2] init: replace sys_mount() to do_mount() 2010-08-17 13:41 ` Arnd Bergmann @ 2010-08-17 14:38 ` Namhyung Kim 0 siblings, 0 replies; 5+ messages in thread From: Namhyung Kim @ 2010-08-17 14:38 UTC (permalink / raw) To: Arnd Bergmann; +Cc: Ingo Molnar, Andrew Morton, Alexander Viro, linux-kernel sys_mount() just copies all (string) arguments from user space to kernel and calls do_mount(). In this case we have all args in kernel already so there is no need to call sys_mount(). One thing we should take care is 'data' have to be in a page unless it is NULL. Do it manually. Signed-off-by: Namhyung Kim <namhyung@gmail.com> --- I found 3 more calls in init/do_mounts_initrd.c and merged them. Please apply this instead. 2010-08-17 (Tue), 15:41 +0200, Arnd Bergmann: > Maybe you can fix that as well in the same patch and move this safeguard > into the copy_mount_options() function? I guess ideally we'd even mark > the arguments to do_mount() as pointers to const, but that might create > an excessive amount of churn. Arnd, thanks for reviewing and the suggestion but I think that should be in a different patch (set). init/do_mounts.c | 18 ++++++++++++++++-- init/do_mounts_initrd.c | 6 +++--- 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/init/do_mounts.c b/init/do_mounts.c index 02e3ca4..8eabff6 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -217,7 +217,21 @@ static void __init get_fs_names(char *page) static int __init do_mount_root(char *name, char *fs, int flags, void *data) { - int err = sys_mount(name, "/root", fs, flags, data); + int err; + unsigned long data_page = 0; + + if (data) { + /* data should be in a page */ + data_page = __get_free_page(GFP_KERNEL); + if (!data_page) + return -ENOMEM; + strlcpy((char *) data_page, data, PAGE_SIZE); + } + + err = do_mount(name, "/root", fs, flags, (void *) data_page); + + if (data_page) + free_page(data_page); if (err) return err; @@ -417,6 +431,6 @@ void __init prepare_namespace(void) mount_root(); out: devtmpfs_mount("dev"); - sys_mount(".", "/", NULL, MS_MOVE, NULL); + do_mount(".", "/", NULL, MS_MOVE, NULL); sys_chroot("."); } diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 2b10853..8355501 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -48,7 +48,7 @@ static void __init handle_initrd(void) old_fd = sys_open("/old", 0, 0); /* move initrd over / and chdir/chroot in initrd root */ sys_chdir("/root"); - sys_mount(".", "/", NULL, MS_MOVE, NULL); + do_mount(".", "/", NULL, MS_MOVE, NULL); sys_chroot("."); /* @@ -66,7 +66,7 @@ static void __init handle_initrd(void) /* move initrd to rootfs' /old */ sys_fchdir(old_fd); - sys_mount("/", ".", NULL, MS_MOVE, NULL); + do_mount("/", ".", NULL, MS_MOVE, NULL); /* switch root and cwd back to / of rootfs */ sys_fchdir(root_fd); sys_chroot("."); @@ -82,7 +82,7 @@ static void __init handle_initrd(void) mount_root(); printk(KERN_NOTICE "Trying to move old root to /initrd ... "); - error = sys_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL); + error = do_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL); if (!error) printk("okay\n"); else { -- 1.7.0.4 ^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2010-08-17 14:38 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2010-08-17 12:37 [PATCH] init/do_mounts.c: replace sys_mount() to do_mount() Namhyung Kim 2010-08-17 13:15 ` Arnd Bergmann 2010-08-17 13:25 ` Namhyung Kim 2010-08-17 13:41 ` Arnd Bergmann 2010-08-17 14:38 ` [PATCH v2] init: " Namhyung Kim
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