After finding a super block in a device also validate its
checksum. This validation is done in the kernel but it was
missing in btrfs-progs.
The function btrfs_check_super_csum() is imported from the
file fs/btrfs/disk-io.c in the kernel source tree.
Signed-off-by: Filipe David Borba Manana <fdman...@gmail.com>
---
disk-io.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 62 insertions(+), 14 deletions(-)
diff --git a/disk-io.c b/disk-io.c
index bd9cf4e..edd4d52 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -1085,47 +1085,95 @@ struct btrfs_root *open_ctree_fd(int fp, const char
*path, u64 sb_bytenr,
return info->fs_root;
}
+static int btrfs_check_super_csum(char *raw_disk_sb)
+{
+ struct btrfs_super_block *disk_sb =
+ (struct btrfs_super_block *)raw_disk_sb;
+ u16 csum_type = btrfs_super_csum_type(disk_sb);
+ int ret = 0;
+
+ if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
+ u32 crc = ~(u32)0;
+ const int csum_size = sizeof(crc);
+ char result[csum_size];
+
+ /*
+ * The super_block structure does not span the whole
+ * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space
+ * is filled with zeros and is included in the checkum.
+ */
+ crc = btrfs_csum_data(NULL, raw_disk_sb + BTRFS_CSUM_SIZE,
+ crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+ btrfs_csum_final(crc, result);
+
+ if (memcmp(raw_disk_sb, result, csum_size))
+ ret = 1;
+
+ if (ret && btrfs_super_generation(disk_sb) < 10) {
+ fprintf(stderr, "btrfs: super block crcs don't match, "
+ "older mkfs detected\n");
+ ret = 0;
+ }
+ }
+
+ if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {
+ fprintf(stderr, "btrfs: unsupported checksum algorithm %u\n",
+ csum_type);
+ ret = 1;
+ }
+
+ return ret;
+}
+
int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr)
{
u8 fsid[BTRFS_FSID_SIZE];
int fsid_is_initialized = 0;
- struct btrfs_super_block buf;
+ char buf[BTRFS_SUPER_INFO_SIZE];
+ struct btrfs_super_block *tmp_sb;
int i;
int ret;
u64 transid = 0;
u64 bytenr;
if (sb_bytenr != BTRFS_SUPER_INFO_OFFSET) {
- ret = pread64(fd, &buf, sizeof(buf), sb_bytenr);
+ ret = pread64(fd, buf, sizeof(buf), sb_bytenr);
if (ret < sizeof(buf))
return -1;
- if (btrfs_super_bytenr(&buf) != sb_bytenr ||
- buf.magic != cpu_to_le64(BTRFS_MAGIC))
+ tmp_sb = (struct btrfs_super_block *)buf;
+
+ if (btrfs_super_bytenr(tmp_sb) != sb_bytenr ||
+ tmp_sb->magic != cpu_to_le64(BTRFS_MAGIC) ||
+ btrfs_check_super_csum(buf))
return -1;
- memcpy(sb, &buf, sizeof(*sb));
+ memcpy(sb, buf, sizeof(*sb));
return 0;
}
for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
bytenr = btrfs_sb_offset(i);
- ret = pread64(fd, &buf, sizeof(buf), bytenr);
+ ret = pread64(fd, buf, sizeof(buf), bytenr);
if (ret < sizeof(buf))
break;
- if (btrfs_super_bytenr(&buf) != bytenr )
+ tmp_sb = (struct btrfs_super_block *)buf;
+
+ if (btrfs_super_bytenr(tmp_sb) != bytenr )
continue;
/* if magic is NULL, the device was removed */
- if (buf.magic == 0 && i == 0)
+ if (tmp_sb->magic == 0 && i == 0)
return -1;
- if (buf.magic != cpu_to_le64(BTRFS_MAGIC))
+ if (tmp_sb->magic != cpu_to_le64(BTRFS_MAGIC))
+ continue;
+ if (btrfs_check_super_csum(buf))
continue;
if (!fsid_is_initialized) {
- memcpy(fsid, buf.fsid, sizeof(fsid));
+ memcpy(fsid, tmp_sb->fsid, sizeof(fsid));
fsid_is_initialized = 1;
- } else if (memcmp(fsid, buf.fsid, sizeof(fsid))) {
+ } else if (memcmp(fsid, tmp_sb->fsid, sizeof(fsid))) {
/*
* the superblocks (the original one and
* its backups) contain data of different
@@ -1134,9 +1182,9 @@ int btrfs_read_dev_super(int fd, struct btrfs_super_block
*sb, u64 sb_bytenr)
continue;
}
- if (btrfs_super_generation(&buf) > transid) {
- memcpy(sb, &buf, sizeof(*sb));
- transid = btrfs_super_generation(&buf);
+ if (btrfs_super_generation(tmp_sb) > transid) {
+ memcpy(sb, buf, sizeof(*sb));
+ transid = btrfs_super_generation(tmp_sb);
}
}
--
1.7.9.5
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