Commit dff3a85f authored by Aleksa Sarai's avatar Aleksa Sarai Committed by Christian Brauner
Browse files

sched_setattr: switch to copy_struct_from_user() 



Switch sched_setattr() syscall from it's own copying struct sched_attr
from userspace to the new dedicated copy_struct_from_user() helper.

The change is very straightforward, and helps unify the syscall
interface for struct-from-userspace syscalls. Ideally we could also
unify sched_getattr(2)-style syscalls as well, but unfortunately the
correct semantics for such syscalls are much less clear (see [1] for
more detail). In future we could come up with a more sane idea for how
the syscall interface should look.

[1]: commit 1251201c ("sched/core: Fix uclamp ABI bug, clean up and
     robustify sched_read_attr() ABI logic and code")

Signed-off-by: default avatarAleksa Sarai <cyphar@cyphar.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
[christian.brauner@ubuntu.com: improve commit message]
Link: https://lore.kernel.org/r/20191001011055.19283-4-cyphar@cyphar.com


Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
parent f14c234b

kernel/sched/core.c

+7 −36
Original line number Diff line number Diff line
@@ -5106,9 +5106,6 @@ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *a 
	u32 size;

	int ret;



	if (!access_ok(uattr, SCHED_ATTR_SIZE_VER0))

		return -EFAULT;



	/* Zero the full structure, so that a short copy will be nice: */

	memset(attr, 0, sizeof(*attr));
@@ -5116,44 +5113,18 @@ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *a 
	if (ret)

		return ret;



	/* Bail out on silly large: */

	if (size > PAGE_SIZE)

		goto err_size;



	/* ABI compatibility quirk: */

	if (!size)

		size = SCHED_ATTR_SIZE_VER0;



	if (size < SCHED_ATTR_SIZE_VER0)

	if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)

		goto err_size;



	/*

	 * If we're handed a bigger struct than we know of,

	 * ensure all the unknown bits are 0 - i.e. new

	 * user-space does not rely on any kernel feature

	 * extensions we dont know about yet.

	 */

	if (size > sizeof(*attr)) {

		unsigned char __user *addr;

		unsigned char __user *end;

		unsigned char val;



		addr = (void __user *)uattr + sizeof(*attr);

		end  = (void __user *)uattr + size;



		for (; addr < end; addr++) {

			ret = get_user(val, addr);

			if (ret)

				return ret;

			if (val)

	ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);

	if (ret) {

		if (ret == -E2BIG)

			goto err_size;

		return ret;

	}

		size = sizeof(*attr);

	}



	ret = copy_from_user(attr, uattr, size);

	if (ret)

		return -EFAULT;



	if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&

	    size < SCHED_ATTR_SIZE_VER1)
@@ -5354,7 +5325,7 @@ sched_attr_copy_to_user(struct sched_attr __user *uattr, 
 * sys_sched_getattr - similar to sched_getparam, but with sched_attr

 * @pid: the pid in question.

 * @uattr: structure containing the extended parameters.

 * @usize: sizeof(attr) that user-space knows about, for forwards and backwards compatibility.

 * @usize: sizeof(attr) for fwd/bwd comp.

 * @flags: for future extension.

 */

SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,

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