[PATCH] tools: Fix realloc() use in fdarray__grow()

[Jann Horn <jannh@google.com>]

If `entries != NULL`, then `fda->entries` has been freed, so whatever
happens afterwards, we must store `entries` in `fda->entries`.
If we bail out at the second realloc(), the new allocation will be bigger
than what fda->nr_alloc says, but that's fine.

Fixes: 2171a9256862 ("tools lib fd array: Allow associating an integer cookie with each entry")
Signed-off-by: Jann Horn <jannh@google.com>
---
To the maintainer:
I'm not sure about the etiquette for using CC stable in
patches for somewhat theoretical issues in userland tools;
feel free to tack a CC stable onto this if you think it
should go into stable.

 tools/lib/api/fd/array.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/lib/api/fd/array.c b/tools/lib/api/fd/array.c
index 58d44d5eee31..acf8eca1a94a 100644
--- a/tools/lib/api/fd/array.c
+++ b/tools/lib/api/fd/array.c
@@ -27,15 +27,13 @@ int fdarray__grow(struct fdarray *fda, int nr)
 
 	if (entries == NULL)
 		return -ENOMEM;
+	fda->entries = entries;
 
 	priv = realloc(fda->priv, psize);
-	if (priv == NULL) {
-		free(entries);
+	if (priv == NULL)
 		return -ENOMEM;
-	}
 
 	fda->nr_alloc = nr_alloc;
-	fda->entries  = entries;
 	fda->priv     = priv;
 	return 0;
 }
-- 
2.25.0