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[PATCH v2 07/12] commit: avoid race when creating orphan commits

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Feb 12, 2015, 11:12 UTC
Message-ID
<1423739543-1025-8-git-send-email-mhagger@alum.mit.edu>
In-Reply-To
<1423739543-1025-1-git-send-email-mhagger@alum.mit.edu>

If HEAD doesn't point at anything during the initial check, then we should make sure that it *still* doesn't point at anything when we are ready to update the reference. Otherwise, another process might commit while we are working (e.g., while we are waiting for the user to edit the commit message) and we will silently overwrite it.

This fixes a failing test in t7516.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
---
 builtin/commit.c        | 2 +-
 t/t7516-commit-races.sh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/builtin/commit.c b/builtin/commit.c
index 8afb0ff..682f922 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1766,7 +1766,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	if (!transaction ||
 	    ref_transaction_update(transaction, "HEAD", sha1,
 				   current_head
-				   ? current_head->object.sha1 : NULL,
+				   ? current_head->object.sha1 : null_sha1,
 				   0, sb.buf, &err) ||
 	    ref_transaction_commit(transaction, &err)) {
 		rollback_index_files();
diff --git a/t/t7516-commit-races.sh b/t/t7516-commit-races.sh
index 08e6a6c..dd44ef2 100755
--- a/t/t7516-commit-races.sh
+++ b/t/t7516-commit-races.sh
@@ -12,7 +12,7 @@ test_expect_success 'set up editor' '
 	EOF
 '
 
-test_expect_failure 'race to create orphan commit' '
+test_expect_success 'race to create orphan commit' '
 	test_must_fail env EDITOR=./editor git commit --allow-empty &&
 	git show -s --pretty=format:%s >subject &&
 	grep -q hare subject &&
-- 
2.1.4
Previous: Michael HaggertyNext: Junio C Hamano
Message 19 of 27 in “Allow reference values to be checked in a transaction”
  1. 00/12 Allow reference values to be checked in a transactionMichael Haggerty, Feb 12, 2015
  2. 01/12 refs: move REF_DELETING to refs.cMichael Haggerty, Feb 12, 2015
  3. 02/12 refs: remove the gap in the REF_* constant valuesMichael Haggerty, Feb 12, 2015
  4. 03/12 struct ref_update: move "have_old" into "flags"Michael Haggerty, Feb 12, 2015
  5. Stefan BellerFeb 12, 2015
  6. Junio C HamanoFeb 12, 2015
  7. Michael HaggertyFeb 17, 2015
  8. Junio C HamanoFeb 17, 2015
  9. 04/12 ref_transaction_update(): remove "have_old" parameterMichael Haggerty, Feb 12, 2015
  10. Junio C HamanoFeb 12, 2015
  11. Michael HaggertyFeb 13, 2015
  12. Junio C HamanoFeb 13, 2015
  13. 05/12 ref_transaction_delete(): remove "have_old" parameterMichael Haggerty, Feb 12, 2015
  14. 06/12 commit: add tests of commit racesMichael Haggerty, Feb 12, 2015
  15. Stefan BellerFeb 12, 2015
  16. Michael HaggertyFeb 17, 2015
  17. Junio C HamanoFeb 12, 2015
  18. Michael HaggertyFeb 17, 2015
  19. 07/12 commit: avoid race when creating orphan commitsMichael Haggerty, Feb 12, 2015
  20. Junio C HamanoFeb 12, 2015
  21. 08/12 ref_transaction_create(): check that new_sha1 is validMichael Haggerty, Feb 12, 2015
  22. 09/12 ref_transaction_delete(): check that old_sha1 is not null_sha1Michael Haggerty, Feb 12, 2015
  23. 10/12 ref_transaction_verify(): new function to check a reference's valueMichael Haggerty, Feb 12, 2015
  24. Stefan BellerFeb 12, 2015
  25. 11/12 update_ref(): improve documentationMichael Haggerty, Feb 12, 2015
  26. 12/12 refs.h: Remove duplication in function docstringsMichael Haggerty, Feb 12, 2015
  27. Junio C HamanoFeb 12, 2015

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