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vfs: allocate page instead of names_cache buffer in mount_block_root

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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.

Change-Id: Ic4539226aa0562b82513be29ddcaee1ef88584f2
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 Artem Borisov
parent 3df0a6646d
commit db18c8e1e5
2 changed files with 5 additions and 5 deletions
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3
include/linux/fs.h
View file

@ -2128,8 +2128,7 @@ extern struct kmem_cache *names_cachep;
extern void final_putname(struct filename *name); extern void final_putname(struct filename *name);
#define __getname_gfp(gfp) kmem_cache_alloc(names_cachep, (gfp)) #define __getname() kmem_cache_alloc(names_cachep, GFP_KERNEL)
#define __getname() __getname_gfp(GFP_KERNEL)
#define __putname(name) kmem_cache_free(names_cachep, (void *)(name)) #define __putname(name) kmem_cache_free(names_cachep, (void *)(name))
#ifndef CONFIG_AUDITSYSCALL #ifndef CONFIG_AUDITSYSCALL
#define putname(name) final_putname(name) #define putname(name) final_putname(name)

7
init/do_mounts.c
View file

@ -343,8 +343,9 @@ static int __init do_mount_root(char *name, char *fs, int flags, void *data)
void __init mount_block_root(char *name, int flags) void __init mount_block_root(char *name, int flags)
{ {
char *fs_names = __getname_gfp(GFP_KERNEL struct page *page = alloc_page(GFP_KERNEL |
| __GFP_NOTRACK_FALSE_POSITIVE); __GFP_NOTRACK_FALSE_POSITIVE);
char *fs_names = page_address(page);
char *p; char *p;
#ifdef CONFIG_BLOCK #ifdef CONFIG_BLOCK
char b[BDEVNAME_SIZE]; char b[BDEVNAME_SIZE];
@ -396,7 +397,7 @@ retry:
#endif #endif
panic("VFS: Unable to mount root fs on %s", b); panic("VFS: Unable to mount root fs on %s", b);
out: out:
putname(fs_names); put_page(page);
} }
#ifdef CONFIG_ROOT_NFS #ifdef CONFIG_ROOT_NFS