forked from Imagelibrary/littlefs
scripts: Added better branch cksum checks
If we're fetching branches anyways, we might as well check that the checksums match. This helps protect against infinite loops in B-tree branches. Also fixed an issue where we weren't xoring perturb state on finding an explicit trunk. Note this is equivalent to LFS_M_CKFETCHES in lfs.c. --- This doesn't mean we always need LFS_M_CKFETCHES. Our dbg scripts just need to be a little bit tougher because 1. running tests with -j creates wildly corrupted and entangled littlefs images, and 2. Rbyd.fetch is almost too forgiving in choosing the nearest trunk.
This commit is contained in:
Christopher Haster
@@ -616,13 +616,13 @@ class Rbyd:
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self.trunk)
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@classmethod
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def fetch(cls, f, block_size, blocks, trunk=None):
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def fetch(cls, f, block_size, blocks, trunk=None, cksum=None):
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if isinstance(blocks, int):
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blocks = (blocks,)
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if len(blocks) > 1:
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# fetch all blocks
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rbyds = [cls.fetch(f, block_size, block, trunk)
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rbyds = [cls.fetch(f, block_size, block, trunk, cksum)
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for block in blocks]
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# determine most recent revision
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i = 0
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@@ -654,9 +654,9 @@ class Rbyd:
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# fetch the rbyd
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rev = fromle32(data[0:4])
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cksum = 0
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cksum_ = crc32c(data[0:4])
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cksum__ = cksum_
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cksum_ = 0
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cksum__ = crc32c(data[0:4])
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cksum___ = cksum__
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perturb = False
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eoff = 0
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eoff_ = None
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@@ -670,10 +670,10 @@ class Rbyd:
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while j_ < len(data) and (not trunk or eoff <= trunk):
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# read next tag
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v, tag, w, size, d = fromtag(data[j_:])
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if v != parity(cksum__):
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if v != parity(cksum___):
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break
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cksum__ ^= 0x00000080 if v else 0
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cksum__ = crc32c(data[j_:j_+d], cksum__)
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cksum___ ^= 0x00000080 if v else 0
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cksum___ = crc32c(data[j_:j_+d], cksum___)
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j_ += d
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if not tag & TAG_ALT and j_ + size > len(data):
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break
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@@ -681,22 +681,22 @@ class Rbyd:
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# take care of cksums
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if not tag & TAG_ALT:
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if (tag & 0xff00) != TAG_CKSUM:
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cksum__ = crc32c(data[j_:j_+size], cksum__)
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cksum___ = crc32c(data[j_:j_+size], cksum___)
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# found a cksum?
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else:
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# check cksum
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cksum___ = fromle32(data[j_:j_+4])
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if cksum__ != cksum___:
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cksum____ = fromle32(data[j_:j_+4])
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if cksum___ != cksum____:
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break
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# commit what we have
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eoff = eoff_ if eoff_ else j_ + size
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cksum = cksum_
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cksum_ = cksum__
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trunk_ = trunk__
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weight = weight_
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# update perturb bit
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perturb = tag & TAG_P
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# revert to data cksum and perturb
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cksum__ = cksum_ ^ (0xfca42daf if perturb else 0)
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cksum___ = cksum__ ^ (0xfca42daf if perturb else 0)
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# evaluate trunks
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if (tag & 0xf000) != TAG_CKSUM:
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@@ -720,18 +720,23 @@ class Rbyd:
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if trunk and j_ + size > trunk:
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eoff_ = j_ + size
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eoff = eoff_
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cksum = cksum_
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cksum_ = cksum___ ^ (
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0xfca42daf if perturb else 0)
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trunk_ = trunk__
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weight = weight_
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trunk___ = 0
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# update canonical checksum, xoring out any perturb state
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cksum_ = cksum__ ^ (0xfca42daf if perturb else 0)
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cksum__ = cksum___ ^ (0xfca42daf if perturb else 0)
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if not tag & TAG_ALT:
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j_ += size
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return cls(block, data, rev, eoff, trunk_, weight, cksum)
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# cksum mismatch?
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if cksum is not None and cksum_ != cksum:
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return cls(block, data, rev, 0, 0, 0, cksum_)
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return cls(block, data, rev, eoff, trunk_, weight, cksum_)
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def lookup(self, rid, tag):
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if not self:
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@@ -861,7 +866,7 @@ class Rbyd:
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not depth or depth_ < depth):
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tag, j, d, data = branch
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block, trunk, cksum = frombranch(data)
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rbyd = Rbyd.fetch(f, block_size, block, trunk)
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rbyd = Rbyd.fetch(f, block_size, block, trunk, cksum)
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# corrupted? bail here so we can keep traversing the tree
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if not rbyd:
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@@ -878,7 +883,7 @@ class Rbyd:
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done, rid, tag, w, j, d, data, _ = self.lookup(-1, TAG_MTREE)
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if not done and rid == -1 and tag == TAG_MTREE:
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w, block, trunk, cksum = frombtree(data)
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mtree = Rbyd.fetch(f, block_size, block, trunk)
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mtree = Rbyd.fetch(f, block_size, block, trunk, cksum)
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# corrupted?
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if not mtree:
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return True, -1, 0, None
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@@ -1161,7 +1166,7 @@ def main(disk, mroots=None, *,
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done, rid, tag, w, j, d, data, _ = mroot.lookup(-1, TAG_MTREE)
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if not done and rid == -1 and tag == TAG_MTREE:
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w, block, trunk, cksum = frombtree(data)
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mtree = Rbyd.fetch(f, block_size, block, trunk)
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mtree = Rbyd.fetch(f, block_size, block, trunk, cksum)
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# traverse entries
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mbid = -1
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@@ -1263,7 +1268,7 @@ def main(disk, mroots=None, *,
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# indirect btree?
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elif tag == TAG_BTREE:
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w, block, trunk, cksum = frombtree(data)
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btree = Rbyd.fetch(f, block_size, block, trunk)
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btree = Rbyd.fetch(f, block_size, block, trunk, cksum)
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shrub = False
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else:
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