The patch titled
Subject: fs/exec.c: account for argv/envp pointers
has been added to the -mm tree. Its filename is
exec-account-for-argv-envp-pointers.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/exec-account-for-argv-envp-pointers.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/exec-account-for-argv-envp-pointers.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: fs/exec.c: account for argv/envp pointers
When limiting the argv/envp strings during exec to 1/4 of the stack limit,
the storage of the pointers to the strings was not included. This means
that an exec with huge numbers of tiny strings could eat 1/4 of the stack
limit in strings and then additional space would be later used by the
pointers to the strings. For example, on 32-bit with a 8MB stack rlimit,
an exec with 1677721 single-byte strings would consume less than 2MB of
stack, the max (8MB / 4) amount allowed, but the pointers to the strings
would consume the remaining additional stack space (1677721 * 4 ==
6710884). The result (1677721 + 6710884 == 8388605) would exhaust stack
space entirely. Controlling this stack exhaustion could result in
pathological behavior in setuid binaries (CVE-2017-1000365).
Fixes: b6a2fea39318 ("mm: variable length argument support")
Link: http://lkml.kernel.org/r/20170622001720.GA32173@beast
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Qualys Security Advisory <qsa@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff -puN fs/exec.c~exec-account-for-argv-envp-pointers fs/exec.c
--- a/fs/exec.c~exec-account-for-argv-envp-pointers
+++ a/fs/exec.c
@@ -220,8 +220,18 @@ static struct page *get_arg_page(struct
if (write) {
unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
+ unsigned long ptr_size;
struct rlimit *rlim;
+ /*
+ * Since the stack will hold pointers to the strings, we
+ * must account for them as well.
+ */
+ ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
+ if (ptr_size > ULONG_MAX - size)
+ goto fail;
+ size += ptr_size;
+
acct_arg_size(bprm, size / PAGE_SIZE);
/*
@@ -239,13 +249,15 @@ static struct page *get_arg_page(struct
* to work from.
*/
rlim = current->signal->rlim;
- if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
- put_page(page);
- return NULL;
- }
+ if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4)
+ goto fail;
}
return page;
+
+fail:
+ put_page(page);
+ return NULL;
}
static void put_arg_page(struct page *page)
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
exec-account-for-argv-envp-pointers.patch
binfmt_elf-use-elf_et_dyn_base-only-for-pie.patch
arm-reduce-elf_et_dyn_base.patch
arm64-reduce-elf_et_dyn_base.patch
powerpc-reduce-elf_et_dyn_base.patch
s390-reduce-elf_et_dyn_base.patch
binfmt_elf-safely-increment-argv-pointers.patch
ipc-drop-non-rcu-allocation.patch
ipc-sem-do-not-use-ipc_rcu_free.patch
ipc-shm-do-not-use-ipc_rcu_free.patch
ipc-msg-do-not-use-ipc_rcu_free.patch
ipc-util-drop-ipc_rcu_free.patch
ipc-sem-avoid-ipc_rcu_alloc.patch
ipc-shm-avoid-ipc_rcu_alloc.patch
ipc-msg-avoid-ipc_rcu_alloc.patch
ipc-util-drop-ipc_rcu_alloc.patch
ipc-move-atomic_set-to-where-it-is-needed.patch
ipc-shm-remove-special-shm_alloc-free.patch
ipc-msg-remove-special-msg_alloc-free.patch
ipc-sem-drop-__sem_free.patch
efi-avoid-fortify-checks-in-efi-stub.patch
x86-power-64-use-char-arrays-for-asm-function-names.patch
kexec_file-adjust-declaration-of-kexec_purgatory.patch
ib-rxe-do-not-copy-extra-stack-memory-to-skb.patch