Filipe David Borba Manana
2014-Jan-11 21:27 UTC
[PATCH] 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: Filipe David Borba Manana <fdmanana@gmail.com>
---
fs/btrfs/Kconfig | 3 ++-
fs/btrfs/Makefile | 2 +-
fs/btrfs/extent-tree.c | 6 +++---
fs/btrfs/hash.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/hash.h | 11 ++++++++---
fs/btrfs/super.c | 10 +++++++++-
6 files changed, 72 insertions(+), 9 deletions(-)
create mode 100644 fs/btrfs/hash.c
diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index aa976ec..a66768e 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -1,6 +1,7 @@
config BTRFS_FS
tristate "Btrfs filesystem support"
- select LIBCRC32C
+ select CRYPTO
+ select CRYPTO_CRC32C
select ZLIB_INFLATE
select ZLIB_DEFLATE
select LZO_COMPRESS
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index af7f000..f341a98 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -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
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 77acc08..db19ed7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1072,11 +1072,11 @@ 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;
}
diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
new file mode 100644
index 0000000..033d217
--- /dev/null
+++ b/fs/btrfs/hash.c
@@ -0,0 +1,49 @@
+/*
+ * 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 "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 __exit 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;
+}
diff --git a/fs/btrfs/hash.h b/fs/btrfs/hash.h
index 1d98281..fdd7866 100644
--- a/fs/btrfs/hash.h
+++ b/fs/btrfs/hash.h
@@ -19,10 +19,15 @@
#ifndef __HASH__
#define __HASH__
-#include <linux/crc32c.h>
+int __init btrfs_hash_init(void);
+
+void __exit 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
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 461e41c..f44cc6a 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -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 @@ free_cachep:
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)
--
1.7.9.5
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