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[PATCH v3 08/13] commit: avoid race when creating orphan commits

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Feb 17, 2015, 17:00 UTC
Message-ID
<1424192423-27979-9-git-send-email-mhagger@alum.mit.edu>
In-Reply-To
<1424192423-27979-1-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 ed04d1c..f2ce14e 100755
--- a/t/t7516-commit-races.sh
+++ b/t/t7516-commit-races.sh
@@ -3,7 +3,7 @@
 test_description='git commit races'
 . ./test-lib.sh
 
-test_expect_failure 'race to create orphan commit' '
+test_expect_success 'race to create orphan commit' '
 	write_script hare-editor <<-\EOF &&
 	git commit --allow-empty -m hare
 	EOF
-- 
2.1.4
Previous: Michael HaggertyNext: Michael Haggerty
Message 9 of 15 in “Allow reference values to be checked in a transaction”
  1. 00/13 Allow reference values to be checked in a transactionMichael Haggerty, Feb 17, 2015
  2. 01/13 refs: move REF_DELETING to refs.cMichael Haggerty, Feb 17, 2015
  3. 02/13 refs: remove the gap in the REF_* constant valuesMichael Haggerty, Feb 17, 2015
  4. 03/13 refs.c: Change some "flags" to "unsigned int"Michael Haggerty, Feb 17, 2015
  5. 04/13 struct ref_update: move "have_old" into "flags"Michael Haggerty, Feb 17, 2015
  6. 05/13 ref_transaction_update(): remove "have_old" parameterMichael Haggerty, Feb 17, 2015
  7. 06/13 ref_transaction_delete(): remove "have_old" parameterMichael Haggerty, Feb 17, 2015
  8. 07/13 commit: add tests of commit racesMichael Haggerty, Feb 17, 2015
  9. 08/13 commit: avoid race when creating orphan commitsMichael Haggerty, Feb 17, 2015
  10. 09/13 ref_transaction_create(): check that new_sha1 is validMichael Haggerty, Feb 17, 2015
  11. 10/13 ref_transaction_delete(): check that old_sha1 is not null_sha1Michael Haggerty, Feb 17, 2015
  12. 11/13 ref_transaction_verify(): new function to check a reference's valueMichael Haggerty, Feb 17, 2015
  13. 12/13 update_ref(): improve documentationMichael Haggerty, Feb 17, 2015
  14. 13/13 refs.h: Remove duplication in function docstringsMichael Haggerty, Feb 17, 2015
  15. Junio C HamanoFeb 17, 2015

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