// SPDX-License-Identifier: GPL-2.0
/*
* mpx.c - Memory Protection eXtensions
*
* Copyright (c) 2014, Intel Corporation.
* Qiaowei Ren <qiaowei.ren@intel.com>
* Dave Hansen <dave.hansen@intel.com>
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm_types.h>
#include <linux/mman.h>
#include <linux/syscalls.h>
#include <linux/sched/sysctl.h>
#include <asm/insn.h>
#include <asm/insn-eval.h>
#include <asm/mmu_context.h>
#include <asm/mpx.h>
#include <asm/processor.h>
#include <asm/fpu/internal.h>
#define CREATE_TRACE_POINTS
#include <asm/trace/mpx.h>
static inline unsigned long mpx_bd_size_bytes(struct mm_struct *mm)
{
if (is_64bit_mm(mm))
return MPX_BD_SIZE_BYTES_64;
else
return MPX_BD_SIZE_BYTES_32;
}
static inline unsigned long mpx_bt_size_bytes(struct mm_struct *mm)
{
if (is_64bit_mm(mm))
return MPX_BT_SIZE_BYTES_64;
else
return MPX_BT_SIZE_BYTES_32;
}
/*
* This is really a simplified "vm_mmap". it only handles MPX
* bounds tables (the bounds directory is user-allocated).
*/
static unsigned long mpx_mmap(unsigned long len)
{
struct mm_struct *mm = current->mm;
unsigned long addr, populate;
/* Only bounds table can be allocated here */
if (len != mpx_bt_size_bytes(mm))
return -EINVAL;
down_write(&mm->mmap_sem);
addr = do_mmap(NULL, 0, len, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, VM_MPX, 0, &populate, NULL);
up_write(&mm->mmap_sem);
if (populate)
mm_populate(addr, populate);
return addr;
}
static int mpx_insn_decode(struct insn *insn,
struct pt_regs *regs)
{
unsigned char buf[MAX_INSN_SIZE];
int x86_64 = !test_thread_flag(TIF_IA32);
int not_copied;
int nr_copied;
not_copied = copy_from_user(buf, (void __user *)regs->ip, sizeof(buf));
nr_copied = sizeof(buf) - not_copied;
/*
* The decoder _should_ fail nicely if we pass it a short buffer.
* But, let's not depend on that implementation detail. If we
* did not get anything, just error out now.
*/
if (!nr_copied)
return -EFAULT;
insn_init(insn, buf, nr_copied, x86_64);
insn_get_length(insn);
/*
* copy_from_user() tries to get as many bytes as we could see in
* the largest possible instruction. If the instruction we are
* after is shorter than that _and_ we attempt to copy from
* something unreadable, we might get a short read. This is OK
* as long as the read did not stop in the middle of the
* instruction. Check to see if we got a partial instruction.
*/
if (nr_copied < insn->length)
return -EFAULT;
insn_get_opcode(insn);
/*
* We only _really_ need to decode bndcl/bndcn/bndcu
* Error out on anything else.
*/
if (insn->opcode.bytes[0] != 0x0f)
goto bad_opcode;
if ((insn->opcode.bytes[1] != 0x1a) &&
(insn->opcode.bytes[1] != 0x1b))
goto bad_opcode;
return 0;
bad_opcode:
return -EINVAL;
}
/*
* If a bounds overflow occurs then a #BR is generated. This
* function decodes MPX instructions to get violation address
* and set this address into extended struct siginfo.
*
* Note that this is not a super precise way of doing this.
* Userspace could have, by the time we get here, written
* anything it wants in to the instructions. We can not
* trust anything about it. They might not be valid
* instructions or might encode invalid registers, etc...
*/
int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs)
{
const struct mpx_bndreg_state *bndregs;
const struct mpx_bndreg *bndreg;
struct insn insn;
uint8_t bndregno;
int err;
err = mpx_insn_decode(&insn, regs);
if (err)
goto err_out;
/*
* We know at this point that we are only dealing with
* MPX instructions.
*/
insn_get_modrm(&insn);
bndregno = X86_MODRM_REG(insn.modrm.value);
if (bndregno > 3) {
err = -EINVAL;
goto err_out;
}
/* get bndregs field from current task's xsave area */
bndregs = get_xsave_field_ptr(XFEATURE_BNDREGS);
if (!bndregs) {
err = -EINVAL;
goto err_out;
}
/* now go select the individual register in the set of 4 */
bndreg = &bndregs->bndreg[bndregno];
/*
* The registers are always 64-bit, but the upper 32
* bits are ignored in 32-bit mode. Also, note that the
* upper bounds are architecturally represented in 1's
* complement form.
*
* The 'unsigned long' cast is because the compiler
* complains when casting from integers to different-size
* pointers.
*/
info->lower = (void __user *)(unsigned long)bndreg->lower_bound;
info->upper = (void __user *)(unsigned long)~bndreg->upper_bound;
info->addr = insn_get_addr_ref(&insn, regs);
/*
* We were not able to extract an address from the instruction,
* probably because there was something invalid in it.
*/
if (info->addr == (void __user *)-1) {
err = -EINVAL;
goto err_out;
}
trace_mpx_bounds_register_exception(info->addr, bndreg);
return 0;
err_out:
/* info might be NULL, but kfree() handles that */
return err;
}
static __user void *mpx_get_bounds_dir(void)
{
const struct mpx_bndcsr *bndcsr;
if (!cpu_feature_enabled(X86_FEATURE_MPX))
return MPX_INVALID_BOUNDS_DIR;
/*
* The bounds directory pointer is stored in a register
* only accessible if we first do an xsave.
*/
bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR);
if (!bndcsr)
return MPX_INVALID_BOUNDS_DIR;
/*
* Make sure the register looks valid by checking the
* enable bit.
*/
if (!(bndcsr->bndcfgu & MPX_BNDCFG_ENABLE_FLAG))
return MPX_INVALID_BOUNDS_DIR;
/*
* Lastly, mask off the low bits used for configuration
* flags, and return the address of the bounds table.
*/
return (void __user *)(unsigned long)
(bndcsr->bndcfgu & MPX_BNDCFG_ADDR_MASK);
}
int mpx_enable_management(void)
{
void __user *bd_base = MPX_INVALID_BOUNDS_DIR;
struct mm_struct *mm = current->mm;
int ret = 0;
/*
* runtime in the userspace will be responsible for allocation of
* the bounds directory. Then, it will save the base of the bounds
* directory into XSAVE/XRSTOR Save Area and enable MPX through
* XRSTOR instruction.
*
* The copy_xregs_to_kernel() beneath get_xsave_field_ptr() is
* expected to be relatively expensive. Storing the bounds
* directory here means that we do not have to do xsave in the
* unmap path; we can just use mm->context.bd_addr instead.
*/
bd_base = mpx_get_bounds_dir();
down_write(&mm->mmap_sem);
/* MPX doesn't support addresses above 47 bits yet. */
if (find_vma(mm, DEFAULT_MAP_WINDOW)) {
pr_warn_once("%s (%d): MPX cannot handle addresses "
"above 47-bits. Disabling.",
current->comm, current->pid);
ret = -ENXIO;
goto out;
}
mm->context.bd_addr = bd_base;
if (mm->context.bd_addr == MPX_INVALID_BOUNDS_DIR)
ret = -ENXIO;
out:
up_write(&mm->mmap_sem);
return ret;
}
int mpx_disable_management(void)
{
struct mm_struct *mm = current->mm;
if (!cpu_feature_enabled(X86_FEATURE_MPX))
return -ENXIO;
down_write(&mm->mmap_sem);
mm->context.bd_addr = MPX_INVALID_BOUNDS_DIR;
up_write(&mm->mmap_sem);
return 0;
}
static int mpx_cmpxchg_bd_entry(struct mm_struct *mm,
unsigned long *curval,
unsigned long __user *addr,
unsigned long old_val, unsigned long new_val)
{
int ret;
/*
* user_atomic_cmpxchg_inatomic() actually uses sizeof()
* the pointer that we pass to it to figure out how much
* data to cmpxchg. We have to be careful here not to
* pass a pointer to a 64-bit data type when we only want
* a 32-bit copy.
*/
if (is_64bit_mm(mm)) {
ret = user_atomic_cmpxchg_inatomic(curval,
addr, old_val, new_val);
} else {
u32 uninitialized_var(curval_32);
u32 old_val_32 = old_val;
u32 new_val_32 = new_val;
u32 __user *addr_32 = (u32 __user *)addr;
ret = user_atomic_cmpxchg_inatomic(&curval_32,
addr_32, old_val_32, new_val_32);
*curval = curval_32;
}
return ret;
}
/*
* With 32-bit mode, a bounds directory is 4MB, and the size of each
* bounds table is 16KB. With 64-bit mode, a bounds directory is 2GB,
* and the size of each bounds table is 4MB.
*/
static int allocate_bt(struct mm_struct *mm, long __user *bd_entry)
{
unsigned long expected_old_val = 0;
unsigned long actual_old_val = 0;
unsigned long bt_addr;
unsigned long bd_new_entry;
int ret = 0;
/*
* Carve the virtual space out of userspace for the new
* bounds table:
*/
bt_addr = mpx_mmap(mpx_bt_size_bytes(mm));
if (IS_ERR((void *)bt_addr))
return PTR_ERR((void *)bt_addr);
/*
* Set the valid flag (kinda like _PAGE_PRESENT in a pte)
*/
bd_new_entry = bt_addr | MPX_BD_ENTRY_VALID_FLAG;
/*
* Go poke the address of the new bounds table in to the
* bounds directory entry out in userspace memory. Note:
* we may race with another CPU instantiating the same table.
* In that case the cmpxchg will see an unexpected
* 'actual_old_val'.
*
* This can fault, but that's OK because we do not hold
* mmap_sem at this point, unlike some of the other part
* of the MPX code that have to pagefault_disable().
*/
ret = mpx_cmpxchg_bd_entry(mm, &actual_old_val, bd_entry,
expected_old_val, bd_new_entry);
if (ret)
goto out_unmap;
/*
* The user_atomic_cmpxchg_inatomic() will only return nonzero
* for faults, *not* if the cmpxchg itself fails. Now we must
* verify that the cmpxchg itself completed successfully.
*/
/*
* We expected an empty 'expected_old_val', but instead found
* an apparently valid entry. Assume we raced with another
* thread to instantiate this table and desclare succecss.
*/
if (actual_old_val & MPX_BD_ENTRY_VALID_FLAG) {
ret = 0;
goto out_unmap;
}
/*
* We found a non-empty bd_entry but it did not have the
* VALID_FLAG set. Return an error which will result in
* a SEGV since this probably means that somebody scribbled
* some invalid data in to a bounds table.
*/
if (expected_old_val != actual_old_val) {
ret = -EINVAL;
goto out_unmap;
}
trace_mpx_new_bounds_table(bt_addr);
return 0;
out_unmap:
vm_munmap(bt_addr, mpx_bt_size_bytes(mm));
return ret;
}
/*
* When a BNDSTX instruction attempts to save bounds to a bounds
* table, it will first attempt to look up the table in the
* first-level bounds directory. If it does not find a table in
* the directory, a #BR is generated and we get here in order to
* allocate a new table.
*
* With 32-bit mode, the size of BD is 4MB, and the size of each
* bound table is 16KB. With 64-bit mode, the size of BD is 2GB,
* and the size of each bound table is 4MB.
*/
static int do_mpx_bt_fault(void)
{
unsigned long bd_entry, bd_base;
const struct mpx_bndcsr *bndcsr;
struct mm_struct *mm = current->mm;
bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR);
if (!bndcsr)
return -EINVAL;
/*
* Mask off the preserve and enable bits
*/
bd_base = bndcsr->bndcfgu & MPX_BNDCFG_ADDR_MASK;
/*
* The hardware provides the address of the missing or invalid
* entry via BNDSTATUS, so we don't have to go look it up.
*/
bd_entry = bndcsr->bndstatus & MPX_BNDSTA_ADDR_MASK;
/*
* Make sure the directory entry is within where we think
* the directory is.
*/
if ((bd_entry < bd_base) ||
(bd_entry >= bd_base + mpx_bd_size_bytes(mm)))
return -EINVAL;
return allocate_bt(mm, (long __user *)bd_entry);
}
int mpx_handle_bd_fault(void)
{
/*
* Userspace never asked us to manage the bounds tables,
* so refuse to help.
*/
if (!kernel_managing_mpx_tables(current->mm))
return -EINVAL;
return do_mpx_bt_fault();
}
/*
* A thin wrapper around get_user_pages(). Returns 0 if the
* fault was resolved or -errno if not.
*/
static int mpx_resolve_fault(long __user *addr, int write)
{
long gup_ret;
int nr_pages = 1;
gup_ret = get_user_pages((unsigned long)addr, nr_pages,
write ? FOLL_WRITE : 0, NULL, NULL);
/*
* get_user_pages() returns number of pages gotten.
* 0 means we failed to fault in and get anything,
* probably because 'addr' is bad.
*/
if (!gup_ret)
return -EFAULT;
/* Other error, return it */
if (gup_ret < 0)
return gup_ret;
/* must have gup'd a page and gup_ret>0, success */
return 0;
}
static unsigned long mpx_bd_entry_to_bt_addr(struct mm_struct *mm,
unsigned long bd_entry)
{
unsigned long bt_addr = bd_entry;
int align_to_bytes;
/*
* Bit 0 in a bt_entry is always the valid bit.
*/
bt_addr &= ~MPX_BD_ENTRY_VALID_FLAG;
/*
* Tables are naturally aligned at 8-byte boundaries
* on 64-bit and 4-byte boundaries on 32-bit. The
* documentation makes it appear that the low bits
* are ignored by the hardware, so we do the same.
*/
if (is_64bit_mm(mm))
align_to_bytes = 8;
else
align_to_bytes = 4;
bt_addr &= ~(align_to_bytes-1);
return bt_addr;
}
/*
* We only want to do a 4-byte get_user() on 32-bit. Otherwise,
* we might run off the end of the bounds table if we are on
* a 64-bit kernel and try to get 8 bytes.
*/
static int get_user_bd_entry(struct mm_struct *mm, unsigned long *bd_entry_ret,
long __user *bd_entry_ptr)
{
u32 bd_entry_32;
int ret;
if (is_64bit_mm(mm))
return get_user(*bd_entry_ret, bd_entry_ptr);
/*
* Note that get_user() uses the type of the *pointer* to
* establish the size of the get, not the destination.
*/
ret = get_user(bd_entry_32, (u32 __user *)bd_entry_ptr);
*bd_entry_ret = bd_entry_32;
return ret;
}
/*
* Get the base of bounds tables pointed by specific bounds
* directory entry.
*/
static int get_bt_addr(struct mm_struct *mm,
long __user *bd_entry_ptr,
unsigned long *bt_addr_result)
{
int ret;
int valid_bit;
unsigned long bd_entry;
unsigned long bt_addr;
if (!access_ok((bd_entry_ptr), sizeof(*bd_entry_ptr)))
return -EFAULT;
while (1) {
int need_write = 0;
pagefault_disable();
ret = get_user_bd_entry(mm, &bd_entry, bd_entry_ptr);
pagefault_enable();
if (!ret)
break;
if (ret == -EFAULT)
ret = mpx_resolve_fault(bd_entry_ptr, need_write);
/*
* If we could not resolve the fault, consider it
* userspace's fault and error out.
*/
if (ret)
return ret;
}
valid_bit = bd_entry & MPX_BD_ENTRY_VALID_FLAG;
bt_addr = mpx_bd_entry_to_bt_addr(mm, bd_entry);
/*
* When the kernel is managing bounds tables, a bounds directory
* entry will either have a valid address (plus the valid bit)
* *OR* be completely empty. If we see a !valid entry *and* some
* data in the address field, we know something is wrong. This
* -EINVAL return will cause a SIGSEGV.
*/
if (!valid_bit && bt_addr)
return -EINVAL;
/*
* Do we have an completely zeroed bt entry? That is OK. It
* just means there was no bounds table for this memory. Make
* sure to distinguish this from -EINVAL, which will cause
* a SEGV.
*/
if (!valid_bit)
return -ENOENT;
*bt_addr_result = bt_addr;
return 0;
}
static inline int bt_entry_size_bytes(struct mm_struct *mm)
{
if (is_64bit_mm(mm))
return MPX_BT_ENTRY_BYTES_64;
else
return MPX_BT_ENTRY_BYTES_32;
}
/*
* Take a virtual address and turns it in to the offset in bytes
* inside of the bounds table where the bounds table entry
* controlling 'addr' can be found.
*/
static unsigned long mpx_get_bt_entry_offset_bytes(struct mm_struct *mm,
unsigned long addr)
{
unsigned long bt_table_nr_entries;
unsigned long offset = addr;
if (is_64bit_mm(mm)) {
/* Bottom 3 bits are ignored on 64-bit */
offset >>= 3;
bt_table_nr_entries = MPX_BT_NR_ENTRIES_64;
} else {
/* Bottom 2 bits are ignored on 32-bit */
offset >>= 2;
bt_table_nr_entries = MPX_BT_NR_ENTRIES_32;
}
/*
* We know the size of the table in to which we are
* indexing, and we have eliminated all the low bits
* which are ignored for indexing.
*
* Mask out all the high bits which we do not need
* to index in to the table. Note that the tables
* are always powers of two so this gives us a proper
* mask.
*/
offset &= (bt_table_nr_entries-1);
/*
* We now have an entry offset in terms of *entries* in
* the table. We need to scale it back up to bytes.
*/
offset *= bt_entry_size_bytes(mm);
return offset;
}
/*
* How much virtual address space does a single bounds
* directory entry cover?
*
* Note, we need a long long because 4GB doesn't fit in
* to a long on 32-bit.
*/
static inline unsigned long bd_entry_virt_space(struct mm_struct *mm)
{
unsigned long long virt_space;
unsigned long long GB = (1ULL << 30);
/*
* This covers 32-bit emulation as well as 32-bit kernels
* running on 64-bit hardware.
*/
if (!is_64bit_mm(mm))
return (4ULL * GB) / MPX_BD_NR_ENTRIES_32;
/*
* 'x86_virt_bits' returns what the hardware is capable
* of, and returns the full >32-bit address space when
* running 32-bit kernels on 64-bit hardware.
*/
virt_space = (1ULL << boot_cpu_data.x86_virt_bits);
return virt_space / MPX_BD_NR_ENTRIES_64;
}
/*
* Free the backing physical pages of bounds table 'bt_addr'.
* Assume start...end is within that bounds table.
*/
static noinline int zap_bt_entries_mapping(struct mm_struct *mm,
unsigned long bt_addr,
unsigned long start_mapping, unsigned long end_mapping)
{
struct vm_area_struct *vma;
unsigned long addr, len;
unsigned long start;
unsigned long end;
/*
* if we 'end' on a boundary, the offset will be 0 which
* is not what we want. Back it up a byte to get the
* last bt entry. Then once we have the entry itself,
* move 'end' back up by the table entry size.
*/
start = bt_addr + mpx_get_bt_entry_offset_bytes(mm, start_mapping);
end = bt_addr + mpx_get_bt_entry_offset_bytes(mm, end_mapping - 1);
/*
* Move end back up by one entry. Among other things
* this ensures that it remains page-aligned and does
* not screw up zap_page_range()
*/
end += bt_entry_size_bytes(mm);
/*
* Find the first overlapping vma. If vma->vm_start > start, there
* will be a hole in the bounds table. This -EINVAL return will
* cause a SIGSEGV.
*/
vma = find_vma(mm, start);
if (!vma || vma->vm_start > start)
return -EINVAL;
/*
* A NUMA policy on a VM_MPX VMA could cause this bounds table to
* be split. So we need to look across the entire 'start -> end'
* range of this bounds table, find all of the VM_MPX VMAs, and
* zap only those.
*/
addr = start;
while (vma && vma->vm_start < end) {
/*
* We followed a bounds directory entry down
* here. If we find a non-MPX VMA, that's bad,
* so stop immediately and return an error. This
* probably results in a SIGSEGV.
*/
if (!(vma->vm_flags & VM_MPX))
return -EINVAL;
len = min(vma->vm_end, end) - addr;
zap_page_range(vma, addr, len);
trace_mpx_unmap_zap(addr, addr+len);
vma = vma->vm_next;
addr = vma->vm_start;
}
return 0;
}
static unsigned long mpx_get_bd_entry_offset(struct mm_struct *mm,
unsigned long addr)
{
/*
* There are several ways to derive the bd offsets. We
* use the following approach here:
* 1. We know the size of the virtual address space
* 2. We know the number of entries in a bounds table
* 3. We know that each entry covers a fixed amount of
* virtual address space.
* So, we can just divide the virtual address by the
* virtual space used by one entry to determine which
* entry "controls" the given virtual address.
*/
if (is_64bit_mm(mm)) {
int bd_entry_size = 8; /* 64-bit pointer */
/*
* Take the 64-bit addressing hole in to account.
*/
addr &= ((1UL << boot_cpu_data.x86_virt_bits) - 1);
return (addr / bd_entry_virt_space(mm)) * bd_entry_size;
} else {
int bd_entry_size = 4; /* 32-bit pointer */
/*
* 32-bit has no hole so this case needs no mask
*/
return (addr / bd_entry_virt_space(mm)) * bd_entry_size;
}
/*
* The two return calls above are exact copies. If we
* pull out a single copy and put it in here, gcc won't
* realize that we're doing a power-of-2 divide and use
* shifts. It uses a real divide. If we put them up
* there, it manages to figure it out (gcc 4.8.3).
*/
}
static int unmap_entire_bt(struct mm_struct *mm,
long __user *bd_entry, unsigned long bt_addr)
{
unsigned long expected_old_val = bt_addr | MPX_BD_ENTRY_VALID_FLAG;
unsigned long uninitialized_var(actual_old_val);
int ret;
while (1) {
int need_write = 1;
unsigned long cleared_bd_entry = 0;
pagefault_disable();
ret = mpx_cmpxchg_bd_entry(mm, &actual_old_val,
bd_entry, expected_old_val, cleared_bd_entry);
pagefault_enable();
if (!ret)
break;
if (ret == -EFAULT)
ret = mpx_resolve_fault(bd_entry, need_write);
/*
* If we could not resolve the fault, consider it
* userspace's fault and error out.
*/
if (ret)
return ret;
}
/*
* The cmpxchg was performed, check the results.
*/
if (actual_old_val != expected_old_val) {
/*
* Someone else raced with us to unmap the table.
* That is OK, since we were both trying to do
* the same thing. Declare success.
*/
if (!actual_old_val)
return 0;
/*
* Something messed with the bounds directory
* entry. We hold mmap_sem for read or write
* here, so it could not be a _new_ bounds table
* that someone just allocated. Something is
* wrong, so pass up the error and SIGSEGV.
*/
return -EINVAL;
}
/*
* Note, we are likely being called under do_munmap() already. To
* avoid recursion, do_munmap() will check whether it comes
* from one bounds table through VM_MPX flag.
*/
return do_munmap(mm, bt_addr, mpx_bt_size_bytes(mm), NULL);
}
static int try_unmap_single_bt(struct mm_struct *mm,
unsigned long start, unsigned long end)
{
struct vm_area_struct *next;
struct vm_area_struct *prev;
/*
* "bta" == Bounds Table Area: the area controlled by the
* bounds table that we are unmapping.
*/
unsigned long bta_start_vaddr = start & ~(bd_entry_virt_space(mm)-1);
unsigned long bta_end_vaddr = bta_start_vaddr + bd_entry_virt_space(mm);
unsigned long uninitialized_var(bt_addr);
void __user *bde_vaddr;
int ret;
/*
* We already unlinked the VMAs from the mm's rbtree so 'start'
* is guaranteed to be in a hole. This gets us the first VMA
* before the hole in to 'prev' and the next VMA after the hole
* in to 'next'.
*/
next = find_vma_prev(mm, start, &prev);
/*
* Do not count other MPX bounds table VMAs as neighbors.
* Although theoretically possible, we do not allow bounds
* tables for bounds tables so our heads do not explode.
* If we count them as neighbors here, we may end up with
* lots of tables even though we have no actual table
* entries in use.
*/
while (next && (next->vm_flags & VM_MPX))
next = next->vm_next;
while (prev && (prev->vm_flags & VM_MPX))
prev = prev->vm_prev;
/*
* We know 'start' and 'end' lie within an area controlled
* by a single bounds table. See if there are any other
* VMAs controlled by that bounds table. If there are not
* then we can "expand" the are we are unmapping to possibly
* cover the entire table.
*/
next = find_vma_prev(mm, start, &prev);
if ((!prev || prev->vm_end <= bta_start_vaddr) &&
(!next || next->vm_start >= bta_end_vaddr)) {
/*
* No neighbor VMAs controlled by same bounds
* table. Try to unmap the whole thing
*/
start = bta_start_vaddr;
end = bta_end_vaddr;
}
bde_vaddr = mm->context.bd_addr + mpx_get_bd_entry_offset(mm, start);
ret = get_bt_addr(mm, bde_vaddr, &bt_addr);
/*
* No bounds table there, so nothing to unmap.
*/
if (ret == -ENOENT) {
ret = 0;
return 0;
}
if (ret)
return ret;
/*
* We are unmapping an entire table. Either because the
* unmap that started this whole process was large enough
* to cover an entire table, or that the unmap was small
* but was the area covered by a bounds table.
*/
if ((start == bta_start_vaddr) &&
(end == bta_end_vaddr))
return unmap_entire_bt(mm, bde_vaddr, bt_addr);
return zap_bt_entries_mapping(mm, bt_addr, start, end);
}
static int mpx_unmap_tables(struct mm_struct *mm,
unsigned long start, unsigned long end)
{
unsigned long one_unmap_start;
trace_mpx_unmap_search(start, end);
one_unmap_start = start;
while (one_unmap_start < end) {
int ret;
unsigned long next_unmap_start = ALIGN(one_unmap_start+1,
bd_entry_virt_space(mm));
unsigned long one_unmap_end = end;
/*
* if the end is beyond the current bounds table,
* move it back so we only deal with a single one
* at a time
*/
if (one_unmap_end > next_unmap_start)
one_unmap_end = next_unmap_start;
ret = try_unmap_single_bt(mm, one_unmap_start, one_unmap_end);
if (ret)
return ret;
one_unmap_start = next_unmap_start;
}
return 0;
}
/*
* Free unused bounds tables covered in a virtual address region being
* munmap()ed. Assume end > start.
*
* This function will be called by do_munmap(), and the VMAs covering
* the virtual address region start...end have already been split if
* necessary, and the 'vma' is the first vma in this range (start -> end).
*/
void mpx_notify_unmap(struct mm_struct *mm, unsigned long start,
unsigned long end)
{
struct vm_area_struct *vma;
int ret;
/*
* Refuse to do anything unless userspace has asked
* the kernel to help manage the bounds tables,
*/
if (!kernel_managing_mpx_tables(current->mm))
return;
/*
* This will look across the entire 'start -> end' range,
* and find all of the non-VM_MPX VMAs.
*
* To avoid recursion, if a VM_MPX vma is found in the range
* (start->end), we will not continue follow-up work. This
* recursion represents having bounds tables for bounds tables,
* which should not occur normally. Being strict about it here
* helps ensure that we do not have an exploitable stack overflow.
*/
vma = find_vma(mm, start);
while (vma && vma->vm_start < end) {
if (vma->vm_flags & VM_MPX)
return;
vma = vma->vm_next;
}
ret = mpx_unmap_tables(mm, start, end);
if (ret)
force_sig(SIGSEGV);
}
/* MPX cannot handle addresses above 47 bits yet. */
unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len,
unsigned long flags)
{
if (!kernel_managing_mpx_tables(current->mm))
return addr;
if (addr + len <= DEFAULT_MAP_WINDOW)
return addr;
if (flags & MAP_FIXED)
return -ENOMEM;
/*
* Requested len is larger than the whole area we're allowed to map in.
* Resetting hinting address wouldn't do much good -- fail early.
*/
if (len > DEFAULT_MAP_WINDOW)
return -ENOMEM;
/* Look for unmap area within DEFAULT_MAP_WINDOW */
return 0;
}
