linux-hardening - [PATCH v4 4/6] binfmt_elf: Use elf

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Message-Id: <20230929032435.2391507-4-keescook@chromium.org>
Date: Thu, 28 Sep 2023 20:24:32 -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 4/6] binfmt_elf: Use elf_load() for library

While load_elf_library() is a libc5-ism, we can still replace most of
its contents with elf_load() as well, further simplifying the code.

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 | 23 ++++-------------------
 1 file changed, 4 insertions(+), 19 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index db47cb802f89..f8b4747f87ed 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1351,30 +1351,15 @@ static int load_elf_library(struct file *file)
 		eppnt++;
 
 	/* Now use mmap to map the library into memory. */
-	error = vm_mmap(file,
-			ELF_PAGESTART(eppnt->p_vaddr),
-			(eppnt->p_filesz +
-			 ELF_PAGEOFFSET(eppnt->p_vaddr)),
+	error = elf_load(file, ELF_PAGESTART(eppnt->p_vaddr),
+			eppnt,
 			PROT_READ | PROT_WRITE | PROT_EXEC,
 			MAP_FIXED_NOREPLACE | MAP_PRIVATE,
-			(eppnt->p_offset -
-			 ELF_PAGEOFFSET(eppnt->p_vaddr)));
-	if (error != ELF_PAGESTART(eppnt->p_vaddr))
-		goto out_free_ph;
+			0);
 
-	elf_bss = eppnt->p_vaddr + eppnt->p_filesz;
-	if (padzero(elf_bss)) {
-		error = -EFAULT;
+	if (error != ELF_PAGESTART(eppnt->p_vaddr))
 		goto out_free_ph;
-	}
 
-	len = ELF_PAGEALIGN(eppnt->p_filesz + eppnt->p_vaddr);
-	bss = ELF_PAGEALIGN(eppnt->p_memsz + eppnt->p_vaddr);
-	if (bss > len) {
-		error = vm_brk(len, bss - len);
-		if (error)
-			goto out_free_ph;
-	}
 	error = 0;
 
 out_free_ph:
-- 
2.34.1