Commit 52f657e3 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

x86: shadow stacks: proper error handling for mmap lock 



김영민 reports that shstk_pop_sigframe() doesn't check for errors from
mmap_read_lock_killable(), which is a silly oversight, and also shows
that we haven't marked those functions with "__must_check", which would
have immediately caught it.

So let's fix both issues.

Reported-by: default avatar김영민 <osori@hspace.io>
Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarDave Hansen <dave.hansen@intel.com>
Acked-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3036cd0d

arch/x86/kernel/shstk.c

+2 −1
Original line number Diff line number Diff line
@@ -351,7 +351,8 @@ static int shstk_pop_sigframe(unsigned long *ssp) 
	need_to_check_vma = PAGE_ALIGN(*ssp) == *ssp;



	if (need_to_check_vma)

		mmap_read_lock_killable(current->mm);

		if (mmap_read_lock_killable(current->mm))

			return -EINTR;



	err = get_shstk_data(&token_addr, (unsigned long __user *)*ssp);

	if (unlikely(err))

include/linux/mmap_lock.h

+3 −3
Original line number Diff line number Diff line
@@ -546,7 +546,7 @@ static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass) 
	__mmap_lock_trace_acquire_returned(mm, true, true);

}



static inline int mmap_write_lock_killable(struct mm_struct *mm)

static inline int __must_check mmap_write_lock_killable(struct mm_struct *mm)

{

	int ret;
@@ -593,7 +593,7 @@ static inline void mmap_read_lock(struct mm_struct *mm) 
	__mmap_lock_trace_acquire_returned(mm, false, true);

}



static inline int mmap_read_lock_killable(struct mm_struct *mm)

static inline int __must_check mmap_read_lock_killable(struct mm_struct *mm)

{

	int ret;
@@ -603,7 +603,7 @@ static inline int mmap_read_lock_killable(struct mm_struct *mm) 
	return ret;

}



static inline bool mmap_read_trylock(struct mm_struct *mm)

static inline bool __must_check mmap_read_trylock(struct mm_struct *mm)

{

	bool ret;