[PATCH 01/15] reftable/stack: fix error handling in `reftable_stack_init_addition()`

From: Patrick Steinhardt <ps@pks.im>
Date: Mar 18, 2024, 10:52 UTC
Message-ID: <1e39d93a45db502280ecff383d53e0294f969719.1710706118.git.ps@pks.im>
In-Reply-To: <cover.1710706118.git.ps@pks.im>

In `reftable_stack_init_addition()` we call `stack_uptodate()` after having created the lockfile to check whether the stack was modified concurrently, which is indicated by a positive return code from the latter function. If so, we return a `REFTABLE_LOCK_ERROR` to the caller and abort the addition.

The error handling has an off-by-one though because we check whether the error code is `> 1` instead of `> 0`. Thus, instead of returning the locking error, we would return a positive value. One of the callers of `reftable_stack_init_addition()` works around this bug by repeating the error code check without the off-by-one. But other callers are subtly broken by this bug.

Fix this by checking for `err > 0` instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 reftable/stack.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/reftable/stack.c b/reftable/stack.c
index 1ecf1b9751..92d9a7facb 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -590,8 +590,7 @@ static int reftable_stack_init_addition(struct reftable_addition *add,
 	err = stack_uptodate(st);
 	if (err < 0)
 		goto done;
-
-	if (err > 1) {
+	if (err > 0) {
 		err = REFTABLE_LOCK_ERROR;
 		goto done;
 	}
@@ -713,10 +712,6 @@ static int stack_try_add(struct reftable_stack *st,
 	int err = reftable_stack_init_addition(&add, st);
 	if (err < 0)
 		goto done;
-	if (err > 0) {
-		err = REFTABLE_LOCK_ERROR;
-		goto done;
-	}
 
 	err = reftable_addition_add(&add, write_table, arg);
 	if (err < 0)

-- 
2.44.0