exec: introduce finalize_exec() before start_thread()

Provide a final callback into fs/exec.c before start_thread() takes
over, to handle any last-minute changes, like the coming restoration of
the stack limit.

Link: http://lkml.kernel.org/r/1518638796-20819-3-git-send-email-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Greg KH <greg@kroah.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index ce1824f..c3deb2e 100644 (file)
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -330,6 +330,7 @@ beyond_if:
 #ifdef __alpha__
        regs->gp = ex.a_gpvalue;
 #endif
+       finalize_exec(bprm);
        start_thread(regs, ex.a_entry, current->mm->start_stack);
        return 0;
 }

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index bdb2012..3edca6c 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1155,6 +1155,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
        ELF_PLAT_INIT(regs, reloc_func_desc);
 #endif
 
+       finalize_exec(bprm);
        start_thread(regs, elf_entry, bprm->p);
        retval = 0;
 out:

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 429326b..d90993a 100644 (file)
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -463,6 +463,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
                            dynaddr);
 #endif
 
+       finalize_exec(bprm);
        /* everything is now ready... get the userspace context ready to roll */
        entryaddr = interp_params.entry_addr ?: exec_params.entry_addr;
        start_thread(regs, entryaddr, current->mm->start_stack);

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 5d6b944..82a48e8 100644 (file)
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -994,6 +994,7 @@ static int load_flat_binary(struct linux_binprm *bprm)
        FLAT_PLAT_INIT(regs);
 #endif
 
+       finalize_exec(bprm);
        pr_debug("start_thread(regs=0x%p, entry=0x%lx, start_stack=0x%lx)\n",
                 regs, start_addr, current->mm->start_stack);
        start_thread(regs, start_addr, current->mm->start_stack);

diff --git a/fs/exec.c b/fs/exec.c
index f4469ab..422ad79 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1384,6 +1384,12 @@ void setup_new_exec(struct linux_binprm * bprm)
 }
 EXPORT_SYMBOL(setup_new_exec);
 
+/* Runs immediately before start_thread() takes over. */
+void finalize_exec(struct linux_binprm *bprm)
+{
+}
+EXPORT_SYMBOL(finalize_exec);
+
 /*
  * Prepare credentials and lock ->cred_guard_mutex.
  * install_exec_creds() commits the new creds and drops the lock.

diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index b0abe21..40e52af 100644 (file)
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -118,6 +118,7 @@ extern int __must_check remove_arg_zero(struct linux_binprm *);
 extern int search_binary_handler(struct linux_binprm *);
 extern int flush_old_exec(struct linux_binprm * bprm);
 extern void setup_new_exec(struct linux_binprm * bprm);
+extern void finalize_exec(struct linux_binprm *bprm);
 extern void would_dump(struct linux_binprm *, struct file *);
 
 extern int suid_dumpable;