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Message-Id: <1518638796-20819-3-git-send-email-keescook@chromium.org>
Date: Wed, 14 Feb 2018 12:06:35 -0800
From: Kees Cook <keescook@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kees Cook <keescook@...omium.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Michal Hocko <mhocko@...nel.org>,
Ben Hutchings <ben@...adent.org.uk>,
Willy Tarreau <w@....eu>,
Hugh Dickins <hughd@...gle.com>,
Oleg Nesterov <oleg@...hat.com>,
"Jason A. Donenfeld" <Jason@...c4.com>,
Rik van Riel <riel@...hat.com>,
Laura Abbott <labbott@...hat.com>,
Greg KH <greg@...ah.com>,
Andy Lutomirski <luto@...nel.org>,
linux-mm@...ck.org,
linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 2/3] exec: Introduce finalize_exec() before start_thread()
Provide a final call back into fs/exec.c before start_thread() takes
over, to handle any last-minute changes, like the coming restoration of
the stack limit.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
As an alternative, fs/exec.c could provide a wrapper for start_thread()...
---
fs/binfmt_aout.c | 1 +
fs/binfmt_elf.c | 1 +
fs/binfmt_elf_fdpic.c | 1 +
fs/binfmt_flat.c | 1 +
fs/exec.c | 6 ++++++
include/linux/binfmts.h | 1 +
6 files changed, 11 insertions(+)
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index ce1824f47ba6..c3deb2e35f20 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -330,6 +330,7 @@ static int load_aout_binary(struct linux_binprm * bprm)
#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 bdb201230bae..3edca6cb9a33 100644
--- 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 429326b6e2e7..d90993adeffa 100644
--- 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 5d6b94475f27..82a48e830018 100644
--- 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 7074913ad2e7..e4ae20ff6278 100644
--- 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 b0abe21d6cc9..40e52afbb2b0 100644
--- 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;
--
2.7.4
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