The patch titled Subject: fs/exec.c: account for argv/envp pointers has been removed from the -mm tree. Its filename was exec-account-for-argv-envp-pointers.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ 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). [akpm@xxxxxxxxxxxxxxxxxxxx: additional commenting from Kees] 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> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Qualys Security Advisory <qsa@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 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 +220,26 @@ 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. + * + * The size calculation is the entire vma while each arg page is + * built, so each time we get here it's calculating how far it + * is currently (rather than each call being just the newly + * added size from the arg page). As a result, we need to + * always add the entire size of the pointers, so that on the + * last call to get_arg_page() we'll actually have the entire + * correct size. + */ + 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 +257,15 @@ 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 mm-allow-slab_nomerge-to-be-set-at-build-time.patch binfmt_elf-use-elf_et_dyn_base-only-for-pie.patch arm-reduce-elf_et_dyn_base.patch arm64-move-elf_et_dyn_base-to-4gb-4mb.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 kexec_file-adjust-declaration-of-kexec_purgatory.patch ib-rxe-do-not-copy-extra-stack-memory-to-skb.patch