Commit 010932f5 authored by ZhangPeng's avatar ZhangPeng Committed by Ma Wupeng
Browse files

userswap: fix VM_BUG_ON() in handle_userfault() 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6CAIM



--------------------------------

When CONFIG_VM_BUG_ON=y and userswap feature is used, there is a kernel
BUG in handle_userfault(). VM_BUG_ON() didn't allow more than one reason
flag.
Fix this by skipping VM_BUG_ON() if reason is VM_UFFD_MISSING|VM_USWAP.

Signed-off-by: default avatarZhangPeng <zhangpeng362@huawei.com>
parent c97cdd7e

fs/userfaultfd.c

+4 −0
Original line number Diff line number Diff line
@@ -406,8 +406,12 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) 


	BUG_ON(ctx->mm != mm);



#ifdef CONFIG_USERSWAP

	VM_BUG_ON(uswap_vm_flag_bug_on(reason));

#else

	VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));

	VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));

#endif



	if (ctx->features & UFFD_FEATURE_SIGBUS)

		goto out;

include/linux/userswap.h

+12 −0
Original line number Diff line number Diff line
@@ -47,6 +47,18 @@ static inline bool uswap_validate_mremap_flags(unsigned long flags) 
	return true;

}



/* When CONFIG_USERSWAP=y, VM_UFFD_MISSING|VM_USWAP is right;

 * 0 or > 1 flags set is a bug; we expect exactly 1.

 */

static inline bool uswap_vm_flag_bug_on(unsigned long reason)

{

	if (reason & ~(VM_UFFD_MISSING | VM_UFFD_WP | VM_USWAP))

		return true;

	if (reason & VM_USWAP)

		return !(reason & VM_UFFD_MISSING) || reason & ~(VM_USWAP|VM_UFFD_MISSING);

	return !(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP);

}



#endif /* CONFIG_USERSWAP */



#endif /* _LINUX_USERSWAP_H */