linux-hardening - [PATCH v4 2/6] binfmt_elf: elf_bss no longer used by load_elf

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Date: Thu, 28 Sep 2023 20:24:30 -0700
From: Kees Cook <keescook@...omium.org>
To: Eric Biederman <ebiederm@...ssion.com>
Cc: Kees Cook <keescook@...omium.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	Sebastian Ott <sebott@...hat.com>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	Pedro Falcato <pedro.falcato@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v4 2/6] binfmt_elf: elf_bss no longer used by load_elf_binary()

With the BSS handled generically via the new filesz/memsz mismatch
handling logic in elf_load(), elf_bss no longer needs to be tracked.
Drop the variable.

Cc: Eric Biederman <ebiederm@...ssion.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-mm@...ck.org
Suggested-by: Eric Biederman <ebiederm@...ssion.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/binfmt_elf.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 2a615f476e44..0214d5a949fc 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -854,7 +854,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long error;
 	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
 	struct elf_phdr *elf_property_phdata = NULL;
-	unsigned long elf_bss, elf_brk;
+	unsigned long elf_brk;
 	int retval, i;
 	unsigned long elf_entry;
 	unsigned long e_entry;
@@ -1045,7 +1045,6 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	if (retval < 0)
 		goto out_free_dentry;
 
-	elf_bss = 0;
 	elf_brk = 0;
 
 	start_code = ~0UL;
@@ -1208,8 +1207,6 @@ static int load_elf_binary(struct linux_binprm *bprm)
 
 		k = elf_ppnt->p_vaddr + elf_ppnt->p_filesz;
 
-		if (k > elf_bss)
-			elf_bss = k;
 		if ((elf_ppnt->p_flags & PF_X) && end_code < k)
 			end_code = k;
 		if (end_data < k)
@@ -1221,7 +1218,6 @@ static int load_elf_binary(struct linux_binprm *bprm)
 
 	e_entry = elf_ex->e_entry + load_bias;
 	phdr_addr += load_bias;
-	elf_bss += load_bias;
 	elf_brk += load_bias;
 	start_code += load_bias;
 	end_code += load_bias;
-- 
2.34.1