vfs: allocate page instead of names_cache buffer in mount_block_root (a608ca21) · Commits · 戴 / test

First, it's incorrect to call putname() after __getname_gfp() since the bare __getname_gfp() call skips the auditing code, while putname() doesn't. mount_block_root allocates a PATH_MAX buffer via __getname_gfp, and then calls get_fs_names to fill the buffer. That function can call get_filesystem_list which assumes that that buffer is a full page in size. On arches where PAGE_SIZE != 4k, then this could potentially overrun. In practice, it's hard to imagine the list of filesystem names even approaching 4k, but it's best to be safe. Just allocate a page for this purpose instead. With this, we can also remove the __getname_gfp() definition since there are no more callers. Signed-off-by:

Jeff Layton <jlayton@redhat.com> Signed-off-by:

Al Viro <viro@zeniv.linux.org.uk>

include/linux/fs.h

+1 −2

Original line number	Diff line number	Diff line
		@@ -2228,8 +2228,7 @@ extern void __init vfs_caches_init(unsigned long);

		extern struct kmem_cache *names_cachep;

		#define __getname_gfp(gfp) kmem_cache_alloc(names_cachep, (gfp))
		#define __getname() __getname_gfp(GFP_KERNEL)
		#define __getname() kmem_cache_alloc(names_cachep, GFP_KERNEL)
		#define __putname(name) kmem_cache_free(names_cachep, (void *)(name))
		#ifndef CONFIG_AUDITSYSCALL
		#define putname(name) __putname(name)

init/do_mounts.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -353,8 +353,9 @@ static int __init do_mount_root(char name, char fs, int flags, void *data)

		void __init mount_block_root(char *name, int flags)
		{
		char *fs_names = __getname_gfp(GFP_KERNEL
		\| __GFP_NOTRACK_FALSE_POSITIVE);
		struct page *page = alloc_page(GFP_KERNEL \|
		__GFP_NOTRACK_FALSE_POSITIVE);
		char *fs_names = page_address(page);
		char *p;
		#ifdef CONFIG_BLOCK
		char b[BDEVNAME_SIZE];
		@@ -406,7 +407,7 @@ retry:
		#endif
		panic("VFS: Unable to mount root fs on %s", b);
		out:
		putname(fs_names);
		put_page(page);
		}

		#ifdef CONFIG_ROOT_NFS

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