linux-kernel - [PATCH] tools/nolibc/stdlib: fix memory error in realloc()

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Date: Tue, 9 Jan 2024 18:44:02 -0500
From: Brennan Xavier McManus <bxmcmanus@...il.com>
To: Willy Tarreau <w@....eu>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
	Ammar Faizi <ammarfaizi2@...weeb.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] tools/nolibc/stdlib: fix memory error in realloc()

Pass user_p_len to memcpy() instead of heap->len to prevent realloc()
from copying an extra sizeof(heap) bytes from beyond the allocated
region.

Signed-off-by: Brennan Xavier McManus <bxmcmanus@...il.com>
---

All tests from Ammar's original test program pass:
https://gist.github.com/ammarfaizi2/db0af6aa0b95a0c7478bce64e349f021
This fix was tested with the following added test for realloc():
https://github.com/brennan913/nolibc-test/blob/main/nolibc_test.c#L73-L120

 tools/include/nolibc/stdlib.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h
index bacfd35c5156..5be9d3c7435a 100644
--- a/tools/include/nolibc/stdlib.h
+++ b/tools/include/nolibc/stdlib.h
@@ -185,7 +185,7 @@ void *realloc(void *old_ptr, size_t new_size)
 	if (__builtin_expect(!ret, 0))
 		return NULL;
 
-	memcpy(ret, heap->user_p, heap->len);
+	memcpy(ret, heap->user_p, user_p_len);
 	munmap(heap, heap->len);
 	return ret;
 }
-- 
2.39.2