There is one report of compressed extent happens in btrfs, but has no
csum and then leads to possible decompress error screwing up kernel
memory.
Although it's a kernel bug, and won't cause problem until compressed
data get corrupted, let's catch such problem in advance.
This patch will catch any unexpected compressed extent with:
1) 0 or less than expected csum
2) nodatasum flag set in the inode item
This is for lowmem mode.
Reported-by: James Harvey <jamespharvey20@xxxxxxxxx>
Issue: #134
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
check/mode-lowmem.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index dac3201b7d99..8e6d5e8de12a 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -1543,6 +1543,24 @@ static int check_file_extent(struct btrfs_root *root, struct btrfs_key *fkey,
csum_found);
}
}
+ /*
+ * Extra check for compressed extents.
+ * Btrfs doesn't allow NODATASUM and compressed extent co-exist, thus
+ * all compressed extent should have csum.
+ */
+ if (compressed && csum_found < search_len) {
+ error(
+"root %llu EXTENT_DATA[%llu %llu] compressed extent must have csum, but only %llu bytes has csum, expect %llu",
+ root->objectid, fkey->objectid, fkey->offset, csum_found,
+ search_len);
+ err |= CSUM_ITEM_MISSING;
+ }
+ if (compressed && nodatasum) {
+ error(
+"root %llu EXTENT_DATA[%llu %llu] is compressed, but inode flag doesn't allow it",
+ root->objectid, fkey->objectid, fkey->offset);
+ err |= FILE_EXTENT_ERROR;
+ }
/* Check EXTENT_DATA hole */
if (!no_holes && *end != fkey->offset) {
--
2.17.0
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