Commit 14a958e6 authored by Filipe David Borba Manana's avatar Filipe David Borba Manana Committed by Chris Mason
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Btrfs: fix btrfs boot when compiled as built-in



After the change titled "Btrfs: add support for inode properties", if
btrfs was built-in the kernel (i.e. not as a module), it would cause a
kernel panic, as reported recently by Fengguang:

[    2.024722] BUG: unable to handle kernel NULL pointer dereference at           (null)
[    2.027814] IP: [<ffffffff81501594>] crc32c+0xc/0x6b
[    2.028684] PGD 0
[    2.028684] Oops: 0000 [#1] SMP
[    2.028684] Modules linked in:
[    2.028684] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc7-04795-ga7b57c2 #1
[    2.028684] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    2.028684] task: ffff88000edba100 ti: ffff88000edd6000 task.ti: ffff88000edd6000
[    2.028684] RIP: 0010:[<ffffffff81501594>]  [<ffffffff81501594>] crc32c+0xc/0x6b
[    2.028684] RSP: 0000:ffff88000edd7e58  EFLAGS: 00010246
[    2.028684] RAX: 0000000000000000 RBX: ffffffff82295550 RCX: 0000000000000000
[    2.028684] RDX: 0000000000000011 RSI: ffffffff81efe393 RDI: 00000000fffffffe
[    2.028684] RBP: ffff88000edd7e60 R08: 0000000000000003 R09: 0000000000015d20
[    2.028684] R10: ffffffff81ef225e R11: ffffffff811b0222 R12: ffffffffffffffff
[    2.028684] R13: 0000000000000239 R14: 0000000000000000 R15: 0000000000000000
[    2.028684] FS:  0000000000000000(0000) GS:ffff88000fa00000(0000) knlGS:0000000000000000
[    2.028684] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[    2.028684] CR2: 0000000000000000 CR3: 000000000220c000 CR4: 00000000000006f0
[    2.028684] Stack:
[    2.028684]  ffffffff82295550 ffff88000edd7e80 ffffffff8238af62 ffffffff8238ac05
[    2.028684]  0000000000000000 ffff88000edd7e98 ffffffff8238ac0f ffffffff8238ac05
[    2.028684]  ffff88000edd7f08 ffffffff810002ba ffff88000edd7f00 ffffffff810e2404
[    2.028684] Call Trace:
[    2.028684]  [<ffffffff8238af62>] btrfs_props_init+0x4f/0x96
[    2.028684]  [<ffffffff8238ac05>] ? ftrace_define_fields_btrfs_space_reservation+0x145/0x145
[    2.028684]  [<ffffffff8238ac0f>] init_btrfs_fs+0xa/0xf0
[    2.028684]  [<ffffffff8238ac05>] ? ftrace_define_fields_btrfs_space_reservation+0x145/0x145
[    2.028684]  [<ffffffff810002ba>] do_one_initcall+0xa4/0x13a
[    2.028684]  [<ffffffff810e2404>] ? parse_args+0x25f/0x33d
[    2.028684]  [<ffffffff8234cf75>] kernel_init_freeable+0x1aa/0x230
[    2.028684]  [<ffffffff8234c785>] ? do_early_param+0x88/0x88
[    2.028684]  [<ffffffff819f61b5>] ? rest_init+0x89/0x89
[    2.028684]  [<ffffffff819f61c3>] kernel_init+0xe/0x109

The issue here is that the initialization function of btrfs (super.c:init_btrfs_fs)
started using crc32c (from lib/libcrc32c.c). But when it needs to call crc32c (as
part of the properties initialization routine), the libcrc32c is not yet initialized,
so crc32c derreferenced a NULL pointer (lib/libcrc32c.c:tfm), causing the kernel
panic on boot.

The approach to fix this is to use crypto component directly to use its crc32c (which
is basically what lib/libcrc32c.c is, a wrapper around crypto). This is what ext4 is
doing as well, it uses crypto directly to get crc32c functionality.

Verified this works both when btrfs is built-in and when it's loadable kernel module.
Signed-off-by: default avatarFilipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent c57c2b3e
config BTRFS_FS
tristate "Btrfs filesystem support"
select LIBCRC32C
select CRYPTO
select CRYPTO_CRC32C
select ZLIB_INFLATE
select ZLIB_DEFLATE
select LZO_COMPRESS
......
......@@ -9,7 +9,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
export.o tree-log.o free-space-cache.o zlib.o lzo.o \
compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
uuid-tree.o props.o
uuid-tree.o props.o hash.o
btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
......
......@@ -1074,11 +1074,11 @@ static u64 hash_extent_data_ref(u64 root_objectid, u64 owner, u64 offset)
__le64 lenum;
lenum = cpu_to_le64(root_objectid);
high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
high_crc = btrfs_crc32c(high_crc, &lenum, sizeof(lenum));
lenum = cpu_to_le64(owner);
low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
lenum = cpu_to_le64(offset);
low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
return ((u64)high_crc << 31) ^ (u64)low_crc;
}
......
/*
* Copyright (C) 2014 Filipe David Borba Manana <fdmanana@gmail.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <crypto/hash.h>
#include <linux/err.h>
#include "hash.h"
static struct crypto_shash *tfm;
int __init btrfs_hash_init(void)
{
tfm = crypto_alloc_shash("crc32c", 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
return 0;
}
void btrfs_hash_exit(void)
{
crypto_free_shash(tfm);
}
u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length)
{
struct {
struct shash_desc shash;
char ctx[crypto_shash_descsize(tfm)];
} desc;
int err;
desc.shash.tfm = tfm;
desc.shash.flags = 0;
*(u32 *)desc.ctx = crc;
err = crypto_shash_update(&desc.shash, address, length);
BUG_ON(err);
return *(u32 *)desc.ctx;
}
......@@ -19,10 +19,15 @@
#ifndef __HASH__
#define __HASH__
#include <linux/crc32c.h>
int __init btrfs_hash_init(void);
void btrfs_hash_exit(void);
u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length);
static inline u64 btrfs_name_hash(const char *name, int len)
{
return crc32c((u32)~1, name, len);
return btrfs_crc32c((u32)~1, name, len);
}
/*
......@@ -31,7 +36,7 @@ static inline u64 btrfs_name_hash(const char *name, int len)
static inline u64 btrfs_extref_hash(u64 parent_objectid, const char *name,
int len)
{
return (u64) crc32c(parent_objectid, name, len);
return (u64) btrfs_crc32c(parent_objectid, name, len);
}
#endif
......@@ -48,6 +48,7 @@
#include "transaction.h"
#include "btrfs_inode.h"
#include "print-tree.h"
#include "hash.h"
#include "props.h"
#include "xattr.h"
#include "volumes.h"
......@@ -1866,11 +1867,15 @@ static int __init init_btrfs_fs(void)
{
int err;
err = btrfs_hash_init();
if (err)
return err;
btrfs_props_init();
err = btrfs_init_sysfs();
if (err)
return err;
goto free_hash;
btrfs_init_compress();
......@@ -1945,6 +1950,8 @@ static int __init init_btrfs_fs(void)
free_compress:
btrfs_exit_compress();
btrfs_exit_sysfs();
free_hash:
btrfs_hash_exit();
return err;
}
......@@ -1963,6 +1970,7 @@ static void __exit exit_btrfs_fs(void)
btrfs_exit_sysfs();
btrfs_cleanup_fs_uuids();
btrfs_exit_compress();
btrfs_hash_exit();
}
module_init(init_btrfs_fs)
......
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