[PATCH] objtool: Fix memory leak in elf_alloc_reloc() on realloc failure

[PATCH] objtool: Fix memory leak in elf_alloc_reloc() on realloc failure

[Weigang He]

When realloc() fails in elf_alloc_reloc(), the original buffer pointer
is overwritten with NULL before the failure is detected. This causes
the original buffer to become unreachable, resulting in a memory leak.

Fix this by using a temporary variable to hold the realloc() result.
If realloc() fails, free the original buffer and set d_buf to NULL to
maintain the expected error state before returning -1.

This bug is found by my static analysis tool and my code review.

Signed-off-by: Weigang He <geoffreyhe2@gmail.com>
---
 tools/objtool/elf.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 6a8ed9c62323e..e47c5c4f25314 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1521,12 +1521,15 @@ static int elf_alloc_reloc(struct elf *elf, struct section *rsec)
 		memcpy(rsec->data->d_buf, orig_buf,
 		       nr_relocs_old * elf_rela_size(elf));
 	} else {
-		rsec->data->d_buf = realloc(rsec->data->d_buf,
-					    nr_alloc * elf_rela_size(elf));
-		if (!rsec->data->d_buf) {
+		void *new_d_buf = realloc(rsec->data->d_buf,
+					  nr_alloc * elf_rela_size(elf));
+		if (!new_d_buf) {
 			ERROR_GLIBC("realloc");
+			free(rsec->data->d_buf);
+			rsec->data->d_buf = NULL;
 			return -1;
 		}
+		rsec->data->d_buf = new_d_buf;
 	}
 
 	rsec->nr_alloc_relocs = nr_alloc;
-- 
2.34.1

Re: [PATCH] objtool: Fix memory leak in elf_alloc_reloc() on realloc failure

[Markus Elfring]

…
> This bug is found by my static analysis tool …

* Did it get a special name?

* Was any additional background information published for such a source code
  analysis tool?


Regards,
Markus

Re: [PATCH] objtool: Fix memory leak in elf_alloc_reloc() on realloc failure

[Peter Zijlstra]

On Sun, Jan 18, 2026 at 06:56:43AM +0000, Weigang He wrote:
> When realloc() fails in elf_alloc_reloc(), the original buffer pointer
> is overwritten with NULL before the failure is detected. This causes
> the original buffer to become unreachable, resulting in a memory leak.
> 
> Fix this by using a temporary variable to hold the realloc() result.
> If realloc() fails, free the original buffer and set d_buf to NULL to
> maintain the expected error state before returning -1.
> 
> This bug is found by my static analysis tool and my code review.

Yeah, except that the moment this error is actually hit, the tool will
exit, freeing all memory.