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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

fs/btrfs/Kconfig

+2 −1
Original line number Diff line number Diff line 
config BTRFS_FS

	tristate "Btrfs filesystem support"

	select LIBCRC32C

	select CRYPTO

	select CRYPTO_CRC32C

	select ZLIB_INFLATE

	select ZLIB_DEFLATE

	select LZO_COMPRESS

fs/btrfs/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

fs/btrfs/extent-tree.c

+3 −3
Original line number Diff line number Diff line
@@ -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;

}

fs/btrfs/hash.c

0 → 100644
+50 −0
Original line number Diff line number Diff line 
/*

 * 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;

}

fs/btrfs/hash.h

+8 −3
Original line number Diff line number Diff line
@@ -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