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[PATCH 2/2] fsck: handle bad trees like other errors

From
David Turner <novalis@novalis.org>
Date
Sep 26, 2016, 19:32 UTC
Message-ID
<1474918365-10937-3-git-send-email-novalis@novalis.org>
In-Reply-To
<1474918365-10937-1-git-send-email-novalis@novalis.org>
From: David Turner <dturner@twosigma.com>

Instead of dying when fsck hits a malformed tree object, log the error like any other and continue. Now fsck can tell the user which tree is bad, too.

Signed-off-by: David Turner <dturner@twosigma.com>
---
 fsck.c                                             |  18 +++--
 t/t1450-fsck.sh                                    |  17 ++++-
 .../307e300745b82417cc1a903f875c7d22e45ef907       |   4 +
 .../f506a346749bb96f52d8605ffba9fb93d46b5ffd       | Bin 0 -> 45 bytes
 tree-walk.c                                        |  83 ++++++++++++++++++---
 tree-walk.h                                        |   8 ++
 6 files changed, 111 insertions(+), 19 deletions(-)
 create mode 100644 t/t1450/bad-objects/307e300745b82417cc1a903f875c7d22e45ef907
 create mode 100644 t/t1450/bad-objects/f506a346749bb96f52d8605ffba9fb93d46b5ffd
diff --git a/fsck.c b/fsck.c
index c9cf3de..4a3069e 100644
--- a/fsck.c
+++ b/fsck.c
@@ -347,8 +347,9 @@ static int fsck_walk_tree(struct tree *tree, void *data, struct fsck_options *op
 		return -1;
 
 	name = get_object_name(options, &tree->object);
-	init_tree_desc(&desc, tree->buffer, tree->size);
-	while (tree_entry(&desc, &entry)) {
+	if (init_tree_desc_gently(&desc, tree->buffer, tree->size))
+		return -1;
+	while (tree_entry_gently(&desc, &entry)) {
 		struct object *obj;
 		int result;
 
@@ -520,7 +521,7 @@ static int verify_ordered(unsigned mode1, const char *name1, unsigned mode2, con
 
 static int fsck_tree(struct tree *item, struct fsck_options *options)
 {
-	int retval;
+	int retval = 0;
 	int has_null_sha1 = 0;
 	int has_full_path = 0;
 	int has_empty_name = 0;
@@ -535,7 +536,10 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 	unsigned o_mode;
 	const char *o_name;
 
-	init_tree_desc(&desc, item->buffer, item->size);
+	if (init_tree_desc_gently(&desc, item->buffer, item->size)) {
+		retval += report(options, &item->object, FSCK_MSG_BAD_TREE, "cannot be parsed as a tree");
+		return retval;
+	}
 
 	o_mode = 0;
 	o_name = NULL;
@@ -556,7 +560,10 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 			       is_hfs_dotgit(name) ||
 			       is_ntfs_dotgit(name));
 		has_zero_pad |= *(char *)desc.buffer == '0';
-		update_tree_entry(&desc);
+		if (update_tree_entry_gently(&desc)) {
+			retval += report(options, &item->object, FSCK_MSG_BAD_TREE, "cannot be parsed as a tree");
+			break;
+		}
 
 		switch (mode) {
 		/*
@@ -597,7 +604,6 @@ static int fsck_tree(struct tree *item, struct fsck_options *options)
 		o_name = name;
 	}
 
-	retval = 0;
 	if (has_null_sha1)
 		retval += report(options, &item->object, FSCK_MSG_NULL_SHA1, "contains entries pointing to null sha1");
 	if (has_full_path)
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 8f52da2..f456963 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -188,8 +188,7 @@ test_expect_success 'commit with NUL in header' '
 	grep "error in commit $new.*unterminated header: NUL at offset" out
 '
 
-test_expect_success 'malformatted tree object' '
-	test_when_finished "git update-ref -d refs/tags/wrong" &&
+test_expect_success 'tree object with duplicate entries' '
 	test_when_finished "remove_object \$T" &&
 	T=$(
 		GIT_INDEX_FILE=test-index &&
@@ -208,6 +207,20 @@ test_expect_success 'malformatted tree object' '
 	grep "error in tree .*contains duplicate file entries" out
 '
 
+test_expect_success 'unparseable tree object' '
+	test_when_finished "git update-ref -d refs/heads/wrong" &&
+	test_when_finished "remove_object 307e300745b82417cc1a903f875c7d22e45ef907" &&
+	test_when_finished "remove_object f506a346749bb96f52d8605ffba9fb93d46b5ffd" &&
+	mkdir -p .git/objects/30 mkdir -p .git/objects/f5 &&
+	cp ../t1450/bad-objects/307e300745b82417cc1a903f875c7d22e45ef907 .git/objects/30/7e300745b82417cc1a903f875c7d22e45ef907 &&
+	cp ../t1450/bad-objects/f506a346749bb96f52d8605ffba9fb93d46b5ffd .git/objects/f5/06a346749bb96f52d8605ffba9fb93d46b5ffd &&
+	git update-ref refs/heads/wrong 307e300745b82417cc1a903f875c7d22e45ef907 &&
+	test_must_fail git fsck 2>out &&
+	grep "warning: empty filename in tree entry" out &&
+	grep "f506a346749bb96f52d8605ffba9fb93d46b5ffd" out &&
+	! grep "fatal: empty filename in tree entry" out
+'
+
 test_expect_success 'tag pointing to nonexistent' '
 	cat >invalid-tag <<-\EOF &&
 	object ffffffffffffffffffffffffffffffffffffffff
diff --git a/t/t1450/bad-objects/307e300745b82417cc1a903f875c7d22e45ef907 b/t/t1450/bad-objects/307e300745b82417cc1a903f875c7d22e45ef907
new file mode 100644
index 0000000..6e23d62
--- /dev/null
+++ b/t/t1450/bad-objects/307e300745b82417cc1a903f875c7d22e45ef907
@@ -0,0 +1,4 @@
+xŽA E]sŠ¹€f°@ÄÁ0Z[
+õú¢é	\ýüÅ{ÿižcIòP²÷4Û)Ó+b&ôÙ]êØR`êœ2ܚ¶–)exØ-:xÖ¼ø×%mö×ûž§”ÇHÕd{-áˆ
+Q¿ÍҀè‡w,pë
+ßçâ&ë?Þ
\ No newline at end of file
diff --git a/t/t1450/bad-objects/f506a346749bb96f52d8605ffba9fb93d46b5ffd b/t/t1450/bad-objects/f506a346749bb96f52d8605ffba9fb93d46b5ffd
new file mode 100644
index 0000000000000000000000000000000000000000..9111a7fc3c8578906e13c930a0fbd3cae047762e
GIT binary patch
literal 45
zcmb=Jqpj)X8)~pA!NA18z}PS_p~CF@#W%j<>n*Fxv)5_&?<#!Z>Hoon;loq@NdS%f
B6F2|>

literal 0
HcmV?d00001

diff --git a/tree-walk.c b/tree-walk.c
index ba544cf..0fb830b 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -22,33 +22,60 @@ static const char *get_mode(const char *str, unsigned int *modep)
 	return str;
 }
 
-static void decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size)
+static int decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size, struct strbuf *err)
 {
 	const char *path;
 	unsigned int mode, len;
 
-	if (size < 23 || buf[size - 21])
-		die("too-short tree object");
+	if (size < 23 || buf[size - 21]) {
+		strbuf_addstr(err, "too-short tree object");
+		return -1;
+	}
 
 	path = get_mode(buf, &mode);
-	if (!path)
-		die("malformed mode in tree entry for tree");
-	if (!*path)
-		die("empty filename in tree entry for tree");
+	if (!path) {
+		strbuf_addstr(err, "malformed mode in tree entry");
+		return -1;
+	}
+	if (!*path) {
+		strbuf_addstr(err, "empty filename in tree entry");
+		return -1;
+	}
 	len = strlen(path) + 1;
 
 	/* Initialize the descriptor entry */
 	desc->entry.path = path;
 	desc->entry.mode = canon_mode(mode);
 	desc->entry.oid  = (const struct object_id *)(path + len);
+
+	return 0;
 }
 
-void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
+static int init_tree_desc_internal(struct tree_desc *desc, const void *buffer, unsigned long size, struct strbuf *err)
 {
 	desc->buffer = buffer;
 	desc->size = size;
 	if (size)
-		decode_tree_entry(desc, buffer, size);
+		return decode_tree_entry(desc, buffer, size, err);
+	return 0;
+}
+
+void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
+{
+	struct strbuf err = STRBUF_INIT;
+	if (init_tree_desc_internal(desc, buffer, size, &err))
+		die("%s", err.buf);
+	strbuf_release(&err);
+}
+
+int init_tree_desc_gently(struct tree_desc *desc, const void *buffer, unsigned long size)
+{
+	struct strbuf err = STRBUF_INIT;
+	int result = init_tree_desc_internal(desc, buffer, size, &err);
+	if (result)
+		warning("%s", err.buf);
+	strbuf_release(&err);
+	return result;
 }
 
 void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
@@ -75,7 +102,7 @@ static void entry_extract(struct tree_desc *t, struct name_entry *a)
 	*a = t->entry;
 }
 
-void update_tree_entry(struct tree_desc *desc)
+static int update_tree_entry_internal(struct tree_desc *desc, struct strbuf *err)
 {
 	const void *buf = desc->buffer;
 	const unsigned char *end = desc->entry.oid->hash + 20;
@@ -89,7 +116,30 @@ void update_tree_entry(struct tree_desc *desc)
 	desc->buffer = buf;
 	desc->size = size;
 	if (size)
-		decode_tree_entry(desc, buf, size);
+		return decode_tree_entry(desc, buf, size, err);
+	return 0;
+}
+
+void update_tree_entry(struct tree_desc *desc)
+{
+	struct strbuf err = STRBUF_INIT;
+	if (update_tree_entry_internal(desc, &err))
+		die("%s", err.buf);
+	strbuf_release(&err);
+}
+
+int update_tree_entry_gently(struct tree_desc *desc)
+{
+	struct strbuf err = STRBUF_INIT;
+	if (update_tree_entry_internal(desc, &err)) {
+		warning("%s", err.buf);
+		strbuf_release(&err);
+		/* Stop processing this tree after error */
+		desc->size = 0;
+		return -1;
+	}
+	strbuf_release(&err);
+	return 0;
 }
 
 int tree_entry(struct tree_desc *desc, struct name_entry *entry)
@@ -102,6 +152,17 @@ int tree_entry(struct tree_desc *desc, struct name_entry *entry)
 	return 1;
 }
 
+int tree_entry_gently(struct tree_desc *desc, struct name_entry *entry)
+{
+	if (!desc->size)
+		return 0;
+
+	*entry = desc->entry;
+	if (update_tree_entry_gently(desc))
+		return 0;
+	return 1;
+}
+
 void setup_traverse_info(struct traverse_info *info, const char *base)
 {
 	int pathlen = strlen(base);
diff --git a/tree-walk.h b/tree-walk.h
index 97a7d69..68bb78b 100644
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -25,14 +25,22 @@ static inline int tree_entry_len(const struct name_entry *ne)
 	return (const char *)ne->oid - ne->path - 1;
 }
 
+/*
+ * The _gently versions of these functions warn and return false on a
+ * corrupt tree entry rather than dying,
+ */
+
 void update_tree_entry(struct tree_desc *);
+int update_tree_entry_gently(struct tree_desc *);
 void init_tree_desc(struct tree_desc *desc, const void *buf, unsigned long size);
+int init_tree_desc_gently(struct tree_desc *desc, const void *buf, unsigned long size);
 
 /*
  * Helper function that does both tree_entry_extract() and update_tree_entry()
  * and returns true for success
  */
 int tree_entry(struct tree_desc *, struct name_entry *);
+int tree_entry_gently(struct tree_desc *, struct name_entry *);
 
 void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1);
 

-- 
2.8.0.rc4.22.g8ae061a
Previous: David TurnerNext: Junio C Hamano
Message 6 of 22 in “tree-walk improvements”
  1. 0/2 tree-walk improvementsDavid Turner, Sep 26, 2016
  2. 1/2 tree-walk: be more specific about corrupt tree errorsDavid Turner, Sep 26, 2016
  3. Jeff KingSep 27, 2016
  4. Junio C HamanoSep 27, 2016
  5. David TurnerSep 27, 2016
  6. 2/2 fsck: handle bad trees like other errorsDavid Turner, Sep 26, 2016
  7. Junio C HamanoSep 26, 2016
  8. Junio C HamanoSep 26, 2016
  9. Junio C HamanoSep 26, 2016
  10. Jeff KingSep 27, 2016
  11. David TurnerSep 27, 2016
  12. thoughts on error passing, was Re: [PATCH 2/2] fsck: handle bad trees like other errorsJeff King, Sep 27, 2016
  13. David TurnerSep 27, 2016
  14. Jeff KingSep 28, 2016
  15. Michael HaggertySep 28, 2016
  16. Jeff KingSep 28, 2016
  17. Junio C HamanoSep 28, 2016
  18. Stefan BellerSep 26, 2016
  19. Junio C HamanoSep 26, 2016
  20. David TurnerSep 26, 2016
  21. Junio C HamanoSep 27, 2016
  22. Junio C HamanoSep 26, 2016

Read the whole thread, see it on lore, or plain text.

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