linux-kernel - [PATCH 2/3] ELF: allocate less for static executable

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Message-ID: <20200219185012.GB4871@avx2>
Date:   Wed, 19 Feb 2020 21:50:12 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] ELF: allocate less for static executable

PT_INTERP ELF header can be spared if executable is static.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 fs/binfmt_elf.c |   19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -698,17 +698,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long reloc_func_desc __maybe_unused = 0;
 	int executable_stack = EXSTACK_DEFAULT;
 	struct elfhdr *elf_ex = (struct elfhdr *)bprm->buf;
-	struct elfhdr *interp_elf_ex;
+	struct elfhdr *interp_elf_ex = NULL;
 	struct arch_elf_state arch_state = INIT_ARCH_ELF_STATE;
 	struct mm_struct *mm;
 	struct pt_regs *regs;
 
-	interp_elf_ex = kmalloc(sizeof(*interp_elf_ex), GFP_KERNEL);
-	if (!interp_elf_ex) {
-		retval = -ENOMEM;
-		goto out_ret;
-	}
-
 	retval = -ENOEXEC;
 	/* First of all, some simple consistency checks */
 	if (memcmp(elf_ex->e_ident, ELFMAG, SELFMAG) != 0)
@@ -768,6 +762,12 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		 */
 		would_dump(bprm, interpreter);
 
+		interp_elf_ex = kmalloc(sizeof(*interp_elf_ex), GFP_KERNEL);
+		if (!interp_elf_ex) {
+			retval = -ENOMEM;
+			goto out_free_ph;
+		}
+
 		/* Get the exec headers */
 		retval = elf_read(interpreter, interp_elf_ex,
 				  sizeof(*interp_elf_ex), 0);
@@ -1073,6 +1073,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
 
 		allow_write_access(interpreter);
 		fput(interpreter);
+
+		kfree(interp_elf_ex);
 	} else {
 		elf_entry = e_entry;
 		if (BAD_ADDR(elf_entry)) {
@@ -1151,12 +1153,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	start_thread(regs, elf_entry, bprm->p);
 	retval = 0;
 out:
-	kfree(interp_elf_ex);
-out_ret:
 	return retval;
 
 	/* error cleanup */
 out_free_dentry:
+	kfree(interp_elf_ex);
 	kfree(interp_elf_phdata);
 	allow_write_access(interpreter);
 	if (interpreter)