Commit 2dc164a4 authored by Joel Granados's avatar Joel Granados
Browse files

sysctl: Create converter functions with two new macros 



Eight converter functions are created using two new macros
(SYSCTL_USER_TO_KERN_INT_CONV & SYSCTL_KERN_TO_USER_INT_CONV); they are
called from four pre-existing converter functions: do_proc_dointvec_conv
and do_proc_dointvec{,_userhz,_ms}_jiffies_conv. The function names
generated by the macros are differentiated by a string suffix passed as
the first macro argument.

The SYSCTL_USER_TO_KERN_INT_CONV macro first executes the u_ptr_op
operation, then checks for overflow, assigns sign (-, +) and finally
writes to the kernel var with WRITE_ONCE; it always returns an -EINVAL
when an overflow is detected. The SYSCTL_KERN_TO_USER_INT_CONV uses
READ_ONCE, casts to unsigned long, then executes the k_ptr_op before
assigning the value to the user space buffer.

The overflow check is always done against MAX_INT after applying
{k,u}_ptr_op. This approach avoids rounding or precision errors that
might occur when using the inverse operations.

Signed-off-by: default avatarJoel Granados <joel.granados@kernel.org>
parent 551bf184

kernel/sysctl.c

+61 −70
Original line number Diff line number Diff line
@@ -368,31 +368,65 @@ static void proc_put_char(void **buf, size_t *size, char c) 
	}

}



#define SYSCTL_USER_TO_KERN_INT_CONV(name, u_ptr_op)		\

int sysctl_user_to_kern_int_conv##name(const bool *negp,	\

				       const unsigned long *u_ptr,\

				       int *k_ptr)		\

{								\

	unsigned long u = u_ptr_op(*u_ptr);			\

	if (*negp) {						\

		if (u > (unsigned long) INT_MAX + 1)		\

			return -EINVAL;				\

		WRITE_ONCE(*k_ptr, -u);				\

	} else {						\

		if (u > (unsigned long) INT_MAX)		\

			return -EINVAL;				\

		WRITE_ONCE(*k_ptr, u);				\

	}							\

	return 0;						\

}



#define SYSCTL_KERN_TO_USER_INT_CONV(name, k_ptr_op)		\

int sysctl_kern_to_user_int_conv##name(bool *negp,		\

				       unsigned long *u_ptr,	\

				       const int *k_ptr)	\

{								\

	int val = READ_ONCE(*k_ptr);				\

	if (val < 0) {						\

		*negp = true;					\

		*u_ptr = -k_ptr_op((unsigned long)val);		\

	} else {						\

		*negp = false;					\

		*u_ptr = k_ptr_op((unsigned long)val);		\

	}							\

	return 0;						\

}



#define SYSCTL_CONV_IDENTITY(val) val

#define SYSCTL_CONV_MULT_HZ(val) ((val) * HZ)

#define SYSCTL_CONV_DIV_HZ(val) ((val) / HZ)



static SYSCTL_USER_TO_KERN_INT_CONV(, SYSCTL_CONV_IDENTITY)

static SYSCTL_KERN_TO_USER_INT_CONV(, SYSCTL_CONV_IDENTITY)



static SYSCTL_USER_TO_KERN_INT_CONV(_hz, SYSCTL_CONV_MULT_HZ)

static SYSCTL_KERN_TO_USER_INT_CONV(_hz, SYSCTL_CONV_DIV_HZ)



static SYSCTL_USER_TO_KERN_INT_CONV(_userhz, clock_t_to_jiffies)

static SYSCTL_KERN_TO_USER_INT_CONV(_userhz, jiffies_to_clock_t)



static SYSCTL_USER_TO_KERN_INT_CONV(_ms, msecs_to_jiffies)

static SYSCTL_KERN_TO_USER_INT_CONV(_ms, jiffies_to_msecs)



static int do_proc_dointvec_conv(bool *negp, unsigned long *u_ptr,

				 int *k_ptr, int dir,

				 const struct ctl_table *table)

{

	if (SYSCTL_USER_TO_KERN(dir)) {

		if (*negp) {

			if (*u_ptr > (unsigned long) INT_MAX + 1)

				return -EINVAL;

			WRITE_ONCE(*k_ptr, -*u_ptr);

		} else {

			if (*u_ptr > (unsigned long) INT_MAX)

				return -EINVAL;

			WRITE_ONCE(*k_ptr, *u_ptr);

		}

	} else {

		int val = READ_ONCE(*k_ptr);

		if (val < 0) {

			*negp = true;

			*u_ptr = -(unsigned long)val;

		} else {

			*negp = false;

			*u_ptr = (unsigned long)val;

		}

		return sysctl_user_to_kern_int_conv(negp, u_ptr, k_ptr);

	}

	return 0;



	return sysctl_kern_to_user_int_conv(negp, u_ptr, k_ptr);

}



static int do_proc_douintvec_conv(unsigned long *u_ptr,
@@ -952,31 +986,14 @@ int proc_doulongvec_ms_jiffies_minmax(const struct ctl_table *table, int dir, 
					 lenp, ppos, HZ, 1000l);

}





static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *u_ptr,

					 int *k_ptr, int dir,

					 const struct ctl_table *table)

{

	if (SYSCTL_USER_TO_KERN(dir)) {

		if (*u_ptr > INT_MAX / HZ)

			return 1;

		if (*negp)

			WRITE_ONCE(*k_ptr, -*u_ptr * HZ);

		else

			WRITE_ONCE(*k_ptr, *u_ptr * HZ);

	} else {

		int val = READ_ONCE(*k_ptr);

		unsigned long lval;

		if (val < 0) {

			*negp = true;

			lval = -(unsigned long)val;

		} else {

			*negp = false;

			lval = (unsigned long)val;

		}

		*u_ptr = lval / HZ;

		return sysctl_user_to_kern_int_conv_hz(negp, u_ptr, k_ptr);

	}

	return 0;

	return sysctl_kern_to_user_int_conv_hz(negp, u_ptr, k_ptr);

}



static int do_proc_dointvec_userhz_jiffies_conv(bool *negp, unsigned long *u_ptr,
@@ -984,22 +1001,11 @@ static int do_proc_dointvec_userhz_jiffies_conv(bool *negp, unsigned long *u_ptr 
						const struct ctl_table *table)

{

	if (SYSCTL_USER_TO_KERN(dir)) {

		if (USER_HZ < HZ && (LONG_MAX / HZ) * USER_HZ < *u_ptr)

			return 1;

		*k_ptr = clock_t_to_jiffies(*negp ? -*u_ptr : *u_ptr);

	} else {

		int val = *k_ptr;

		unsigned long lval;

		if (val < 0) {

			*negp = true;

			lval = -(unsigned long)val;

		} else {

			*negp = false;

			lval = (unsigned long)val;

		if (USER_HZ < HZ)

			return -EINVAL;

		return sysctl_user_to_kern_int_conv_userhz(negp, u_ptr, k_ptr);

	}

		*u_ptr = jiffies_to_clock_t(lval);

	}

	return 0;

	return sysctl_kern_to_user_int_conv_userhz(negp, u_ptr, k_ptr);

}



static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *u_ptr,
@@ -1007,24 +1013,9 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *u_ptr, 
					    const struct ctl_table *table)

{

	if (SYSCTL_USER_TO_KERN(dir)) {

		unsigned long jif = msecs_to_jiffies(*negp ? -*u_ptr : *u_ptr);



		if (jif > INT_MAX)

			return 1;

		WRITE_ONCE(*k_ptr, (int)jif);

	} else {

		int val = READ_ONCE(*k_ptr);

		unsigned long lval;

		if (val < 0) {

			*negp = true;

			lval = -(unsigned long)val;

		} else {

			*negp = false;

			lval = (unsigned long)val;

		}

		*u_ptr = jiffies_to_msecs(lval);

		return sysctl_user_to_kern_int_conv_ms(negp, u_ptr, k_ptr);

	}

	return 0;

	return sysctl_kern_to_user_int_conv_ms(negp, u_ptr, k_ptr);

}



static int do_proc_dointvec_ms_jiffies_minmax_conv(bool *negp, unsigned long *u_ptr,