diff options
| author | Kees Cook <keescook@chromium.org> | 2017-07-10 15:52:54 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-10 16:32:36 -0700 |
| commit | 67c6777a5d331dda32a4c4a1bf0cac85bdaaaed8 (patch) | |
| tree | c5ae9869b8e0a3e81091bb08597ea54346655824 /fs/binfmt_elf.c | |
| parent | a73dc5370e153ac63718d850bddf0c9aa9d871e6 (diff) | |
binfmt_elf: safely increment argv pointers
When building the argv/envp pointers, the envp is needlessly
pre-incremented instead of just continuing after the argv pointers are
finished. In some (likely impossible) race where the strings could be
changed from userspace between copy_strings() and here, it might be
possible to confuse the envp position. Instead, just use sp like
everything else.
Link: http://lkml.kernel.org/r/20170622173838.GA43308@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Qualys Security Advisory <qsa@qualys.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/binfmt_elf.c')
| -rw-r--r-- | fs/binfmt_elf.c | 20 |
1 files changed, 9 insertions, 11 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 7465c3ea5dd5..879ff9c7ffd0 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -163,8 +163,6 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, unsigned long p = bprm->p; int argc = bprm->argc; int envc = bprm->envc; - elf_addr_t __user *argv; - elf_addr_t __user *envp; elf_addr_t __user *sp; elf_addr_t __user *u_platform; elf_addr_t __user *u_base_platform; @@ -304,38 +302,38 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, /* Now, let's put argc (and argv, envp if appropriate) on the stack */ if (__put_user(argc, sp++)) return -EFAULT; - argv = sp; - envp = argv + argc + 1; - /* Populate argv and envp */ + /* Populate list of argv pointers back to argv strings. */ p = current->mm->arg_end = current->mm->arg_start; while (argc-- > 0) { size_t len; - if (__put_user((elf_addr_t)p, argv++)) + if (__put_user((elf_addr_t)p, sp++)) return -EFAULT; len = strnlen_user((void __user *)p, MAX_ARG_STRLEN); if (!len || len > MAX_ARG_STRLEN) return -EINVAL; p += len; } - if (__put_user(0, argv)) + if (__put_user(0, sp++)) return -EFAULT; - current->mm->arg_end = current->mm->env_start = p; + current->mm->arg_end = p; + + /* Populate list of envp pointers back to envp strings. */ + current->mm->env_end = current->mm->env_start = p; while (envc-- > 0) { size_t len; - if (__put_user((elf_addr_t)p, envp++)) + if (__put_user((elf_addr_t)p, sp++)) return -EFAULT; len = strnlen_user((void __user *)p, MAX_ARG_STRLEN); if (!len || len > MAX_ARG_STRLEN) return -EINVAL; p += len; } - if (__put_user(0, envp)) + if (__put_user(0, sp++)) return -EFAULT; current->mm->env_end = p; /* Put the elf_info on the stack in the right place. */ - sp = (elf_addr_t __user *)envp + 1; if (copy_to_user(sp, elf_info, ei_index * sizeof(elf_addr_t))) return -EFAULT; return 0; |