Commit 7de7de7c authored Dec 15, 2019 by Linus Torvalds

Fix root mounting with no mount options

The "trivial conversion" in commit cccaa5e3 ("init: use do_mount()
instead of ksys_mount()") was totally broken, since it didn't handle the
case of a NULL mount data pointer.  And while I had "tested" it (and
presumably Dominik had too) that bug was hidden by me having options.

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Reported-by: Ondřej Jirman <megi@xff.cz>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-and-tested-by: Borislav Petkov <bp@suse.de>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Tested-by: Eric Biggers <ebiggers@kernel.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d1eef1c6

init/do_mounts.c

+13 −10

Original line number	Diff line number	Diff line
		@@ -391,17 +391,19 @@ static int __init do_mount_root(const char name, const char fs,
		const int flags, const void *data)
		{
		struct super_block *s;
		char *data_page;
		struct page *p;
		struct page *p = NULL;
		char *data_page = NULL;
		int ret;

		if (data) {
		/* do_mount() requires a full page as fifth argument */
		p = alloc_page(GFP_KERNEL);
		if (!p)
		return -ENOMEM;

		data_page = page_address(p);
		strncpy(data_page, data, PAGE_SIZE - 1);
		/* zero-pad. do_mount() will make sure it's terminated */
		strncpy(data_page, data, PAGE_SIZE);
		}

		ret = do_mount(name, "/root", fs, flags, data_page);
		if (ret)
		@@ -417,6 +419,7 @@ static int __init do_mount_root(const char name, const char fs,
		MAJOR(ROOT_DEV), MINOR(ROOT_DEV));

		out:
		if (p)
		put_page(p);
		return ret;
		}

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