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btrfs-image: Fix a data race in build_chunk_tree.

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A mdrestore_struct was being written to without its mutex being held.
This race was found with ThreadSanitizer; the relevant part of the report
looks like this:

WARNING: ThreadSanitizer: data race (pid=18828)
  Write of size 8 at 0x7fffffc3d088 by main thread:
    #0 build_chunk_tree .../btrfs-progs/btrfs-image.c:2233
    #1 __restore_metadump .../btrfs-progs/btrfs-image.c:2294
    #2 restore_metadump .../btrfs-progs/btrfs-image.c:2345
    #3 main .../btrfs-progs/btrfs-image.c:2545

  Previous read of size 8 at 0x7fffffc3d088 by thread T1 (mutexes: write M0):
    #0 restore_worker .../btrfs-progs/btrfs-image.c:1636

  Location is stack of main thread.

  Mutex M0 created at:
    #0 pthread_mutex_init ??:0
    #1 mdrestore_init .../btrfs-progs/btrfs-image.c:1766
    #2 __restore_metadump .../btrfs-progs/btrfs-image.c:2286
    #3 restore_metadump .../btrfs-progs/btrfs-image.c:2345
    #4 main .../btrfs-progs/btrfs-image.c:2545

  Thread T1 (tid=18830, running) created by main thread at:
    #0 pthread_create ??:0
    #1 mdrestore_init .../btrfs-progs/btrfs-image.c:1784
    #2 __restore_metadump .../btrfs-progs/btrfs-image.c:2286
    #3 restore_metadump .../btrfs-progs/btrfs-image.c:2345
    #4 main .../btrfs-progs/btrfs-image.c:2545

Signed-off-by: Adam Buchbinder <abuchbinder@google.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
This commit is contained in:
Adam Buchbinder 2014-05-18 22:40:42 -07:00 committed by David Sterba
parent 85691ebeac
commit c2429c8a0d
1 changed files with 2 additions and 0 deletions
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2
btrfs-image.c
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@ -2216,6 +2216,7 @@ static int build_chunk_tree(struct mdrestore_struct *mdres,
buffer = tmp;
}
pthread_mutex_lock(&mdres->mutex);
super = (struct btrfs_super_block *)buffer;
chunk_root_bytenr = btrfs_super_chunk_root(super);
mdres->leafsize = btrfs_super_leafsize(super);
@ -2224,6 +2225,7 @@ static int build_chunk_tree(struct mdrestore_struct *mdres,
BTRFS_UUID_SIZE);
mdres->devid = le64_to_cpu(super->dev_item.devid);
free(buffer);
pthread_mutex_unlock(&mdres->mutex);
return search_for_chunk_blocks(mdres, chunk_root_bytenr, 0);
}