[patch 140/166] fs/binfmt_elf.c: allocate less for static executable

Andrew Morton
2020-04-07T03:11:32Z

From: Alexey Dobriyan <adobriyan@gmail.com>
Subject: fs/binfmt_elf.c: allocate less for static executable

PT_INTERP ELF header can be spared if executable is static.

Link: http://lkml.kernel.org/r/20200219185012.GB4871@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/fs/binfmt_elf.c~elf-allocate-less-for-static-executable
+++ a/fs/binfmt_elf.c
@@ -699,17 +699,11 @@ static int load_elf_binary(struct linux_
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)
@@ -769,6 +763,12 @@ static int load_elf_binary(struct linux_
*/
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);
@@ -1074,6 +1074,8 @@ out_free_interp:

allow_write_access(interpreter);
fput(interpreter);
+
+ kfree(interp_elf_ex);
} else {
elf_entry = e_entry;
if (BAD_ADDR(elf_entry)) {
@@ -1152,12 +1154,11 @@ out_free_interp:
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)
_