Commit b394d468 authored by Kees Cook's avatar Kees Cook
Browse files

usercopy: Enhance and rename report_usercopy() 



In preparation for refactoring the usercopy checks to pass offset to
the hardened usercopy report, this renames report_usercopy() to the
more accurate usercopy_abort(), marks it as noreturn because it is,
adds a hopefully helpful comment for anyone investigating such reports,
makes the function available to the slab allocators, and adds new "detail"
and "offset" arguments.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 4f5e8386

include/linux/uaccess.h

+6 −0
Original line number Diff line number Diff line
@@ -273,4 +273,10 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); 
#define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)

#endif



#ifdef CONFIG_HARDENED_USERCOPY

void __noreturn usercopy_abort(const char *name, const char *detail,

			       bool to_user, unsigned long offset,

			       unsigned long len);

#endif



#endif		/* __LINUX_UACCESS_H__ */

mm/usercopy.c

+19 −5
Original line number Diff line number Diff line
@@ -58,11 +58,25 @@ static noinline int check_stack_object(const void *obj, unsigned long len) 
	return GOOD_STACK;

}



static void report_usercopy(unsigned long len, bool to_user, const char *type)

/*

 * If this function is reached, then CONFIG_HARDENED_USERCOPY has found an

 * unexpected state during a copy_from_user() or copy_to_user() call.

 * There are several checks being performed on the buffer by the

 * __check_object_size() function. Normal stack buffer usage should never

 * trip the checks, and kernel text addressing will always trip the check.

 * For cache objects, copies must be within the object size.

 */

void __noreturn usercopy_abort(const char *name, const char *detail,

			       bool to_user, unsigned long offset,

			       unsigned long len)

{

	pr_emerg("kernel memory %s attempt detected %s '%s' (%lu bytes)\n",

	pr_emerg("Kernel memory %s attempt detected %s %s%s%s%s (offset %lu, size %lu)!\n",

		 to_user ? "exposure" : "overwrite",

		to_user ? "from" : "to", type ? : "unknown", len);

		 to_user ? "from" : "to",

		 name ? : "unknown?!",

		 detail ? " '" : "", detail ? : "", detail ? "'" : "",

		 offset, len);



	/*

	 * For greater effect, it would be nice to do do_group_exit(),

	 * but BUG() actually hooks all the lock-breaking and per-arch
@@ -260,6 +274,6 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) 
		return;



report:

	report_usercopy(n, to_user, err);

	usercopy_abort(err, NULL, to_user, 0, n);

}

EXPORT_SYMBOL(__check_object_size);

tools/objtool/check.c

+1 −0
Original line number Diff line number Diff line
@@ -138,6 +138,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func, 
		"__reiserfs_panic",

		"lbug_with_loc",

		"fortify_panic",

		"usercopy_abort",

	};



	if (func->bind == STB_WEAK)

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