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[PATCH 02/17] replace dangerous uses of strbuf_attach

From
Jeff King <peff@peff.net>
Date
Jun 10, 2014, 21:38 UTC
Message-ID
<20140610213838.GB19147@sigill.intra.peff.net>
In-Reply-To
<20140610213509.GA26979@sigill.intra.peff.net>

It is not a good idea to strbuf_attach an arbitrary pointer just because a function you are calling wants a strbuf. Attaching implies a transfer of memory ownership; if anyone were to modify or release the resulting strbuf, we would free() the pointer, leading to possible problems:

  1. Other users of the original pointer might access freed
     memory.
  2. The pointer might not be the start of a malloc'd
     area, so calling free() on it in the first place would
     be wrong.

In the two cases modified here, we are fortunate that nobody touches the strbuf once it is attached, but it is an accident waiting to happen. Since the previous commit, commit_tree and friends take a pointer/buf pair, so we can just do away with the strbufs entirely.

Signed-off-by: Jeff King <peff@peff.net>
---
I also manually checked the other dozen or so calls to strbuf_attach,
and they all look good.
 notes-cache.c | 6 ++----
 notes-merge.c | 5 +----
 2 files changed, 3 insertions(+), 8 deletions(-)
diff --git a/notes-cache.c b/notes-cache.c
index 4ad0799..c4e9bb7 100644
--- a/notes-cache.c
+++ b/notes-cache.c
@@ -48,7 +48,6 @@ int notes_cache_write(struct notes_cache *c)
 {
 	unsigned char tree_sha1[20];
 	unsigned char commit_sha1[20];
-	struct strbuf msg = STRBUF_INIT;
 
 	if (!c || !c->tree.initialized || !c->tree.ref || !*c->tree.ref)
 		return -1;
@@ -57,9 +56,8 @@ int notes_cache_write(struct notes_cache *c)
 
 	if (write_notes_tree(&c->tree, tree_sha1))
 		return -1;
-	strbuf_attach(&msg, c->validity,
-		      strlen(c->validity), strlen(c->validity) + 1);
-	if (commit_tree(msg.buf, msg.len, tree_sha1, NULL, commit_sha1, NULL, NULL) < 0)
+	if (commit_tree(c->validity, strlen(c->validity), tree_sha1, NULL,
+			commit_sha1, NULL, NULL) < 0)
 		return -1;
 	if (update_ref("update notes cache", c->tree.ref, commit_sha1, NULL,
 		       0, UPDATE_REFS_QUIET_ON_ERR) < 0)
diff --git a/notes-merge.c b/notes-merge.c
index 9d94210..697cec3 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -673,7 +673,6 @@ int notes_merge_commit(struct notes_merge_options *o,
 	struct dirent *e;
 	struct strbuf path = STRBUF_INIT;
 	char *msg = strstr(partial_commit->buffer, "\n\n");
-	struct strbuf sb_msg = STRBUF_INIT;
 	int baselen;
 
 	strbuf_addstr(&path, git_path(NOTES_MERGE_WORKTREE));
@@ -720,10 +719,8 @@ int notes_merge_commit(struct notes_merge_options *o,
 		strbuf_setlen(&path, baselen);
 	}
 
-	strbuf_attach(&sb_msg, msg, strlen(msg), strlen(msg) + 1);
 	create_notes_commit(partial_tree, partial_commit->parents,
-			    sb_msg.buf, sb_msg.len,
-			    result_sha1);
+			    msg, strlen(msg), result_sha1);
 	if (o->verbosity >= 4)
 		printf("Finalized notes merge commit: %s\n",
 			sha1_to_hex(result_sha1));

-- 
2.0.0.729.g520999f
Previous: Jeff KingNext: Jeff King
Message 37 of 60 in “store length of commit->buffer”
  1. 0/15 store length of commit->bufferJeff King, Jun 9, 2014
  2. 01/15 alloc: include any-object allocations in alloc_reportJeff King, Jun 9, 2014
  3. 02/15 commit: push commit_index update into alloc_commit_nodeJeff King, Jun 9, 2014
  4. Junio C HamanoJun 10, 2014
  5. 03/15 do not create "struct commit" with xcallocJeff King, Jun 9, 2014
  6. Junio C HamanoJun 10, 2014
  7. Jeff KingJun 10, 2014
  8. 04/15 logmsg_reencode: return const bufferJeff King, Jun 9, 2014
  9. Eric SunshineJun 10, 2014
  10. 05/15 sequencer: use logmsg_reencode in get_messageJeff King, Jun 9, 2014
  11. Junio C HamanoJun 10, 2014
  12. Jeff KingJun 10, 2014
  13. 06/15 provide a helper to free commit bufferJeff King, Jun 9, 2014
  14. 07/15 provide a helper to set the commit bufferJeff King, Jun 9, 2014
  15. 08/15 provide helpers to access the commit bufferJeff King, Jun 9, 2014
  16. Eric SunshineJun 10, 2014
  17. 09/15 use get_cached_commit_buffer where appropriateJeff King, Jun 9, 2014
  18. 10/15 use get_commit_buffer to avoid duplicate codeJeff King, Jun 9, 2014
  19. Eric SunshineJun 10, 2014
  20. Jeff KingJun 10, 2014
  21. 11/15 convert logmsg_reencode to get_commit_bufferJeff King, Jun 9, 2014
  22. 12/15 use get_commit_buffer everywhereJeff King, Jun 9, 2014
  23. Junio C HamanoJun 9, 2014
  24. Jeff KingJun 10, 2014
  25. Jeff KingJun 10, 2014
  26. Junio C HamanoJun 10, 2014
  27. Jeff KingJun 10, 2014
  28. 13/15 commit-slab: provide a static initializerJeff King, Jun 9, 2014
  29. 14/15 commit: convert commit->buffer to a slabJeff King, Jun 9, 2014
  30. 15/15 commit: record buffer length in cacheJeff King, Jun 9, 2014
  31. Christian CouderJun 10, 2014
  32. Jeff KingJun 10, 2014
  33. Jeff KingJun 10, 2014
  34. Christian CouderJun 10, 2014
  35. 0/17 store length of commit->bufferJeff King, Jun 10, 2014
  36. 01/17 commit_tree: take a pointer/len pair rather than a const strbufJeff King, Jun 10, 2014
  37. 02/17 replace dangerous uses of strbuf_attachJeff King, Jun 10, 2014
  38. 03/17 alloc: include any-object allocations in alloc_reportJeff King, Jun 10, 2014
  39. 04/17 commit: push commit_index update into alloc_commit_nodeJeff King, Jun 10, 2014
  40. 05/17 do not create "struct commit" with xcallocJeff King, Jun 10, 2014
  41. 06/17 logmsg_reencode: return const bufferJeff King, Jun 10, 2014
  42. 07/17 sequencer: use logmsg_reencode in get_messageJeff King, Jun 10, 2014
  43. 08/17 provide a helper to free commit bufferJeff King, Jun 10, 2014
  44. Junio C HamanoJun 12, 2014
  45. Jeff KingJun 12, 2014
  46. Jeff KingJun 12, 2014
  47. 09/17 provide a helper to set the commit bufferJeff King, Jun 10, 2014
  48. 10/17 provide helpers to access the commit bufferJeff King, Jun 10, 2014
  49. 11/17 use get_cached_commit_buffer where appropriateJeff King, Jun 10, 2014
  50. 12/17 use get_commit_buffer to avoid duplicate codeJeff King, Jun 10, 2014
  51. 13/17 convert logmsg_reencode to get_commit_bufferJeff King, Jun 10, 2014
  52. 14/17 use get_commit_buffer everywhereJeff King, Jun 10, 2014
  53. 15/17 commit-slab: provide a static initializerJeff King, Jun 10, 2014
  54. Junio C HamanoJun 12, 2014
  55. Jeff KingJun 12, 2014
  56. 16/17 commit: convert commit->buffer to a slabJeff King, Jun 10, 2014
  57. 17/17 commit: record buffer length in cacheJeff King, Jun 10, 2014
  58. Jeff KingJun 10, 2014
  59. Junio C HamanoJun 12, 2014
  60. reuse cached commit buffer when parsing signaturesJeff King, Jun 13, 2014

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