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vfs: allocate page instead of names_cache buffer in mount_block_root 

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>
This commit is contained in:
Jeff Layton 2012-10-10 15:25:26 -04:00 committed by Al Viro
parent 4fa6b5ecbf
commit a608ca21f5
2 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/fs.h
View File

@ -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)

7
init/do_mounts.c
View File

@ -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 @@ void __init mount_block_root(char *name, int flags)
#endif
panic("VFS: Unable to mount root fs on %s", b);
out:
putname(fs_names);
put_page(page);
}
#ifdef CONFIG_ROOT_NFS