Function elf_open_read() only zero initializes the initial part of
allocated struct elf; num_relocs member was recently added outside the
zeroed part so that it was left uninitialized, resulting in build failures
on some systems.

The partial initialization is a relic of times when struct elf had large
hash tables embedded. This is no longer the case so remove the trap and
initialize the whole structure instead.

Fixes: eb0481bbc4ce ("objtool: Fix reloc_hash size")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
---
 tools/objtool/elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index d420b5d2e2b6..081befa4674b 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1005,7 +1005,7 @@ struct elf *elf_open_read(const char *name, int flags)
 		perror("malloc");
 		return NULL;
 	}
-	memset(elf, 0, offsetof(struct elf, sections));
+	memset(elf, 0, sizeof(*elf));
 
 	INIT_LIST_HEAD(&elf->sections);
 
-- 
2.41.0

On Thu, Jun 29, 2023 at 12:05:05PM +0200, Michal Kubecek wrote:
> Function elf_open_read() only zero initializes the initial part of
> allocated struct elf; num_relocs member was recently added outside the
> zeroed part so that it was left uninitialized, resulting in build failures
> on some systems.
> 
> The partial initialization is a relic of times when struct elf had large
> hash tables embedded. This is no longer the case so remove the trap and
> initialize the whole structure instead.
> 
> Fixes: eb0481bbc4ce ("objtool: Fix reloc_hash size")
> Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
> ---
>  tools/objtool/elf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> index d420b5d2e2b6..081befa4674b 100644
> --- a/tools/objtool/elf.c
> +++ b/tools/objtool/elf.c
> @@ -1005,7 +1005,7 @@ struct elf *elf_open_read(const char *name, int flags)
>  		perror("malloc");
>  		return NULL;
>  	}
> -	memset(elf, 0, offsetof(struct elf, sections));
> +	memset(elf, 0, sizeof(*elf));
>  
>  	INIT_LIST_HEAD(&elf->sections);

Thanks!

Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>

-- 
Josh

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     9f71fbcde2820f2af4658313e808cf1e579190a4
Gitweb:        https://git.kernel.org/tip/9f71fbcde2820f2af4658313e808cf1e579190a4
Author:        Michal Kubecek <mkubecek@suse.cz>
AuthorDate:    Thu, 29 Jun 2023 12:05:05 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 10 Jul 2023 09:52:28 +02:00

objtool: initialize all of struct elf

Function elf_open_read() only zero initializes the initial part of
allocated struct elf; num_relocs member was recently added outside the
zeroed part so that it was left uninitialized, resulting in build failures
on some systems.

The partial initialization is a relic of times when struct elf had large
hash tables embedded. This is no longer the case so remove the trap and
initialize the whole structure instead.

Fixes: eb0481bbc4ce ("objtool: Fix reloc_hash size")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20230629102051.42E8360467@lion.mk-sys.cz
---
 tools/objtool/elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index d420b5d..081befa 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1005,7 +1005,7 @@ struct elf *elf_open_read(const char *name, int flags)
 		perror("malloc");
 		return NULL;
 	}
-	memset(elf, 0, offsetof(struct elf, sections));
+	memset(elf, 0, sizeof(*elf));
 
 	INIT_LIST_HEAD(&elf->sections);