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
---
btrfs-image.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/btrfs-image.c b/btrfs-image.c
index cc8627c..017ab1d 100644
--- a/btrfs-image.c
+++ b/btrfs-image.c
@@ -2228,6 +2228,7 @@ 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);
@@ -2236,6 +2237,7 @@ 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);
}
--
1.9.1.423.g4596e3a
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