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Make UMA and malloc(9) return non-executable memory in most cases.

Browse Source 
Most kernel memory that is allocated after boot does not need to be
executable.  There are a few exceptions.  For example, kernel modules
do need executable memory, but they don't use UMA or malloc(9).  The
BPF JIT compiler also needs executable memory and did use malloc(9)
until r317072.

(Note that a side effect of r316767 was that the "small allocation"
path in UMA on amd64 already returned non-executable memory.  This
meant that some calls to malloc(9) or the UMA zone(9) allocator could
return executable memory, while others could return non-executable
memory.  This change makes the behavior consistent.)

This change makes malloc(9) return non-executable memory unless the new
M_EXEC flag is specified.  After this change, the UMA zone(9) allocator
will always return non-executable memory, and a KASSERT will catch
attempts to use the M_EXEC flag to allocate executable memory using
uma_zalloc() or its variants.

Allocations that do need executable memory have various choices.  They
may use the M_EXEC flag to malloc(9), or they may use a different VM
interfact to obtain executable pages.

Now that malloc(9) again allows executable allocations, this change also
reverts most of r317072.

PR:		228927
Reviewed by:	alc, kib, markj, jhb (previous version)
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D15691
This commit is contained in:
Jonathan T. Looney 2018-06-13 17:04:41 +00:00
parent b13a70d5a4
commit 0766f278d8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=335068
16 changed files with 142 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
share/man/man9/malloc.9
View File

@ -29,7 +29,7 @@
.\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
.\" $FreeBSD$
.\"
.Dd January 24, 2018
.Dd June 13, 2018
.Dt MALLOC 9
.Os
.Sh NAME
@ -189,6 +189,11 @@ This option should only be used in combination with
.Dv M_NOWAIT
when an allocation failure cannot be tolerated by the caller without
catastrophic effects on the system.
.It Dv M_EXEC
Indicates that the system should allocate executable memory.
If this flag is not set, the system will not allocate executable memory.
Not all platforms enforce a distinction between executable and
non-executable memory.
.El
.Pp
Exactly one of either

11
share/man/man9/zone.9
View File

@ -25,7 +25,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd April 26, 2017
.Dd June 13, 2018
.Dt ZONE 9
.Os
.Sh NAME
@ -375,6 +375,15 @@ if the zone ran out of unused items
and
.Dv M_NOWAIT
was specified.
.Sh IMPLEMENTATION NOTES
The memory that these allocation calls return is not executable.
The
.Fn uma_zalloc
function does not support the
.Dv M_EXEC
flag to allocate executable memory.
Not all platforms enforce a distinction between executable and
non-executable memory.
.Sh SEE ALSO
.Xr malloc 9
.Sh HISTORY

20
sys/amd64/amd64/bpf_jit_machdep.c
View File

@ -44,9 +44,6 @@ __FBSDID("$FreeBSD$");
#include <sys/socket.h>
#include <net/if.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#else
#include <stdlib.h>
#include <string.h>
@ -605,11 +602,7 @@ bpf_jit_compile(struct bpf_insn *prog, u_int nins, size_t *size)
*size = stream.cur_ip;
#ifdef _KERNEL
/*
* We cannot use malloc(9) because DMAP is mapped as NX.
*/
stream.ibuf = (void *)kmem_malloc(kernel_arena, *size,
M_NOWAIT);
stream.ibuf = malloc(*size, M_BPFJIT, M_EXEC | M_NOWAIT);
if (stream.ibuf == NULL)
break;
#else
@ -658,14 +651,3 @@ bpf_jit_compile(struct bpf_insn *prog, u_int nins, size_t *size)
return ((bpf_filter_func)(void *)stream.ibuf);
}
void
bpf_jit_free(void *func, size_t size)
{
#ifdef _KERNEL
kmem_free(kernel_arena, (vm_offset_t)func, size);
#else
munmap(func, size);
#endif
}

13
sys/i386/i386/bpf_jit_machdep.c
View File

@ -632,7 +632,7 @@ bpf_jit_compile(struct bpf_insn *prog, u_int nins, size_t *size)
*size = stream.cur_ip;
#ifdef _KERNEL
stream.ibuf = malloc(*size, M_BPFJIT, M_NOWAIT);
stream.ibuf = malloc(*size, M_BPFJIT, M_EXEC | M_NOWAIT);
if (stream.ibuf == NULL)
break;
#else
@ -681,14 +681,3 @@ bpf_jit_compile(struct bpf_insn *prog, u_int nins, size_t *size)
return ((bpf_filter_func)(void *)stream.ibuf);
}
void
bpf_jit_free(void *func, size_t size)
{
#ifdef _KERNEL
free(func, M_BPFJIT);
#else
munmap(func, size);
#endif
}

4
sys/kern/kern_malloc.c
View File

@ -564,7 +564,7 @@ void *
return (va);
#endif
if (size <= kmem_zmax) {
if (size <= kmem_zmax && (flags & M_EXEC) == 0) {
if (size & KMEM_ZMASK)
size = (size & ~KMEM_ZMASK) + KMEM_ZBASE;
indx = kmemsize[size >> KMEM_ZSHIFT];
@ -609,7 +609,7 @@ malloc_domain(size_t size, struct malloc_type *mtp, int domain,
if (malloc_dbg(&va, &size, mtp, flags) != 0)
return (va);
#endif
if (size <= kmem_zmax) {
if (size <= kmem_zmax && (flags & M_EXEC) == 0) {
if (size & KMEM_ZMASK)
size = (size & ~KMEM_ZMASK) + KMEM_ZBASE;
indx = kmemsize[size >> KMEM_ZSHIFT];

3
sys/kern/subr_vmem.c
View File

@ -241,6 +241,9 @@ static struct vmem buffer_arena_storage;
static struct vmem transient_arena_storage;
/* kernel and kmem arenas are aliased for backwards KPI compat. */
vmem_t *kernel_arena = &kernel_arena_storage;
#if VM_NRESERVLEVEL > 0
vmem_t *kernel_rwx_arena = NULL;
#endif
vmem_t *kmem_arena = &kernel_arena_storage;
vmem_t *buffer_arena = &buffer_arena_storage;
vmem_t *transient_arena = &transient_arena_storage;

6
sys/net/bpf_jitter.c
View File

@ -101,11 +101,13 @@ void
bpf_destroy_jit_filter(bpf_jit_filter *filter)
{
if (filter->func != bpf_jit_accept_all)
bpf_jit_free(filter->func, filter->size);
#ifdef _KERNEL
if (filter->func != bpf_jit_accept_all)
free(filter->func, M_BPFJIT);
free(filter, M_BPFJIT);
#else
if (filter->func != bpf_jit_accept_all)
munmap(filter->func, filter->size);
free(filter);
#endif
}

1
sys/net/bpf_jitter.h
View File

@ -88,6 +88,5 @@ void bpf_destroy_jit_filter(bpf_jit_filter *filter);
struct bpf_insn;
bpf_filter_func bpf_jit_compile(struct bpf_insn *, u_int, size_t *);
void bpf_jit_free(void *, size_t);
#endif /* _NET_BPF_JITTER_H_ */

3
sys/sys/malloc.h
View File

@ -49,7 +49,7 @@
#define MINALLOCSIZE UMA_SMALLEST_UNIT
/*
* flags to malloc.
* Flags to memory allocation functions.
*/
#define M_NOWAIT 0x0001 /* do not block */
#define M_WAITOK 0x0002 /* ok to block */
@ -59,6 +59,7 @@
#define M_NODUMP 0x0800 /* don't dump pages in this allocation */
#define M_FIRSTFIT 0x1000 /* Only for vmem, fast fit. */
#define M_BESTFIT 0x2000 /* Only for vmem, low fragmentation. */
#define M_EXEC 0x4000 /* allocate executable space. */
#define M_MAGIC 877983977 /* time when first defined :-) */

3
sys/vm/uma.h
View File

@ -617,11 +617,12 @@ void uma_zone_set_freef(uma_zone_t zone, uma_free freef);
* These flags are setable in the allocf and visible in the freef.
*/
#define UMA_SLAB_BOOT 0x01 /* Slab alloced from boot pages */
#define UMA_SLAB_KRWX 0x02 /* Slab alloced from kernel_rwx_arena */
#define UMA_SLAB_KERNEL 0x04 /* Slab alloced from kernel_map */
#define UMA_SLAB_PRIV 0x08 /* Slab alloced from priv allocator */
#define UMA_SLAB_OFFP 0x10 /* Slab is managed separately */
#define UMA_SLAB_MALLOC 0x20 /* Slab is a large malloc slab */
/* 0x02, 0x40 and 0x80 are available */
/* 0x40 and 0x80 are available */
/*
* Used to pre-fill a zone with some number of items

32
sys/vm/uma_core.c
View File

@ -1167,7 +1167,7 @@ page_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
void *p; /* Returned page */
*pflag = UMA_SLAB_KERNEL;
p = (void *) kmem_malloc_domain(domain, bytes, wait);
p = (void *) kmem_malloc_domain(kernel_arena, domain, bytes, wait);
return (p);
}
@ -2280,6 +2280,7 @@ uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
"uma_zalloc_arg: zone \"%s\"", zone->uz_name);
}
KASSERT((flags & M_EXEC) == 0, ("uma_zalloc_arg: called with M_EXEC"));
KASSERT(curthread->td_critnest == 0 || SCHEDULER_STOPPED(),
("uma_zalloc_arg: called with spinlock or critical section held"));
if (zone->uz_flags & UMA_ZONE_PCPU)
@ -3587,20 +3588,34 @@ uma_zone_exhausted_nolock(uma_zone_t zone)
void *
uma_large_malloc_domain(vm_size_t size, int domain, int wait)
{
struct vmem *arena;
vm_offset_t addr;
uma_slab_t slab;
#if VM_NRESERVLEVEL > 0
if (__predict_true((wait & M_EXEC) == 0))
arena = kernel_arena;
else
arena = kernel_rwx_arena;
#else
arena = kernel_arena;
#endif
slab = zone_alloc_item(slabzone, NULL, domain, wait);
if (slab == NULL)
return (NULL);
if (domain == UMA_ANYDOMAIN)
addr = kmem_malloc(kernel_arena, size, wait);
addr = kmem_malloc(arena, size, wait);
else
addr = kmem_malloc_domain(domain, size, wait);
addr = kmem_malloc_domain(arena, domain, size, wait);
if (addr != 0) {
vsetslab(addr, slab);
slab->us_data = (void *)addr;
slab->us_flags = UMA_SLAB_KERNEL | UMA_SLAB_MALLOC;
#if VM_NRESERVLEVEL > 0
if (__predict_false(arena == kernel_rwx_arena))
slab->us_flags |= UMA_SLAB_KRWX;
#endif
slab->us_size = size;
slab->us_domain = vm_phys_domain(PHYS_TO_VM_PAGE(
pmap_kextract(addr)));
@ -3622,10 +3637,19 @@ uma_large_malloc(vm_size_t size, int wait)
void
uma_large_free(uma_slab_t slab)
{
struct vmem *arena;
KASSERT((slab->us_flags & UMA_SLAB_KERNEL) != 0,
("uma_large_free: Memory not allocated with uma_large_malloc."));
kmem_free(kernel_arena, (vm_offset_t)slab->us_data, slab->us_size);
#if VM_NRESERVLEVEL > 0
if (__predict_true((slab->us_flags & UMA_SLAB_KRWX) == 0))
arena = kernel_arena;
else
arena = kernel_rwx_arena;
#else
arena = kernel_arena;
#endif
kmem_free(arena, (vm_offset_t)slab->us_data, slab->us_size);
uma_total_dec(slab->us_size);
zone_free_item(slabzone, slab, NULL, SKIP_NONE);
}

3
sys/vm/vm_extern.h
View File

@ -65,7 +65,8 @@ vm_offset_t kmem_alloc_contig_domain(int domain, vm_size_t size, int flags,
vm_paddr_t low, vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
vm_memattr_t memattr);
vm_offset_t kmem_malloc(struct vmem *, vm_size_t size, int flags);
vm_offset_t kmem_malloc_domain(int domain, vm_size_t size, int flags);
vm_offset_t kmem_malloc_domain(struct vmem *, int domain, vm_size_t size,
int flags);
void kmem_free(struct vmem *, vm_offset_t, vm_size_t);
/* This provides memory for previously allocated address space. */

36
sys/vm/vm_init.c
View File

@ -135,6 +135,23 @@ kva_import(void *unused, vmem_size_t size, int flags, vmem_addr_t *addrp)
return (0);
}
#if VM_NRESERVLEVEL > 0
/*
* Import a superpage from the normal kernel arena into the special
* arena for allocations with different permissions.
*/
static int
kernel_rwx_alloc(void *arena, vmem_size_t size, int flags, vmem_addr_t *addrp)
{
KASSERT((size % KVA_QUANTUM) == 0,
("kernel_rwx_alloc: Size %jd is not a multiple of %d",
(intmax_t)size, (int)KVA_QUANTUM));
return (vmem_xalloc(arena, size, KVA_QUANTUM, 0, 0, VMEM_ADDR_MIN,
VMEM_ADDR_MAX, flags, addrp));
}
#endif
/*
* vm_init initializes the virtual memory system.
* This is done only by the first cpu up.
@ -173,12 +190,31 @@ vm_mem_init(dummy)
vmem_init(kernel_arena, "kernel arena", 0, 0, PAGE_SIZE, 0, 0);
vmem_set_import(kernel_arena, kva_import, NULL, NULL, KVA_QUANTUM);
#if VM_NRESERVLEVEL > 0
/*
* In an architecture with superpages, maintain a separate arena
* for allocations with permissions that differ from the "standard"
* read/write permissions used for memory in the kernel_arena.
*/
kernel_rwx_arena = vmem_create("kernel rwx arena", 0, 0, PAGE_SIZE,
0, M_WAITOK);
vmem_set_import(kernel_rwx_arena, kernel_rwx_alloc,
(vmem_release_t *)vmem_xfree, kernel_arena, KVA_QUANTUM);
#endif
for (domain = 0; domain < vm_ndomains; domain++) {
vm_dom[domain].vmd_kernel_arena = vmem_create(
"kernel arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
vmem_set_import(vm_dom[domain].vmd_kernel_arena,
(vmem_import_t *)vmem_alloc, NULL, kernel_arena,
KVA_QUANTUM);
#if VM_NRESERVLEVEL > 0
vm_dom[domain].vmd_kernel_rwx_arena = vmem_create(
"kernel rwx arena domain", 0, 0, PAGE_SIZE, 0, M_WAITOK);
vmem_set_import(vm_dom[domain].vmd_kernel_rwx_arena,
kernel_rwx_alloc, (vmem_release_t *)vmem_xfree,
vm_dom[domain].vmd_kernel_arena, KVA_QUANTUM);
#endif
}
#ifndef UMA_MD_SMALL_ALLOC

58
sys/vm/vm_kern.c
View File

@ -212,8 +212,8 @@ retry:
if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
m->valid = VM_PAGE_BITS_ALL;
pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
pmap_enter(kernel_pmap, addr + i, m, VM_PROT_RW,
VM_PROT_RW | PMAP_ENTER_WIRED, 0);
}
VM_OBJECT_WUNLOCK(object);
return (addr);
@ -298,8 +298,8 @@ retry:
if ((flags & M_ZERO) && (m->flags & PG_ZERO) == 0)
pmap_zero_page(m);
m->valid = VM_PAGE_BITS_ALL;
pmap_enter(kernel_pmap, tmp, m, VM_PROT_ALL,
VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
pmap_enter(kernel_pmap, tmp, m, VM_PROT_RW,
VM_PROT_RW | PMAP_ENTER_WIRED, 0);
tmp += PAGE_SIZE;
}
VM_OBJECT_WUNLOCK(object);
@ -372,20 +372,32 @@ kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
* Allocate wired-down pages in the kernel's address space.
*/
vm_offset_t
kmem_malloc_domain(int domain, vm_size_t size, int flags)
kmem_malloc_domain(struct vmem *vmem, int domain, vm_size_t size, int flags)
{
vmem_t *vmem;
vmem_t *arena;
vm_offset_t addr;
int rv;
vmem = vm_dom[domain].vmd_kernel_arena;
#if VM_NRESERVLEVEL > 0
KASSERT(vmem == kernel_arena || vmem == kernel_rwx_arena,
("kmem_malloc_domain: Only kernel_arena or kernel_rwx_arena "
"are supported."));
if (__predict_true(vmem == kernel_arena))
arena = vm_dom[domain].vmd_kernel_arena;
else
arena = vm_dom[domain].vmd_kernel_rwx_arena;
#else
KASSERT(vmem == kernel_arena,
("kmem_malloc_domain: Only kernel_arena is supported."));
arena = vm_dom[domain].vmd_kernel_arena;
#endif
size = round_page(size);
if (vmem_alloc(vmem, size, flags | M_BESTFIT, &addr))
if (vmem_alloc(arena, size, flags | M_BESTFIT, &addr))
return (0);
rv = kmem_back_domain(domain, kernel_object, addr, size, flags);
if (rv != KERN_SUCCESS) {
vmem_free(vmem, addr, size);
vmem_free(arena, addr, size);
return (0);
}
return (addr);
@ -398,12 +410,9 @@ kmem_malloc(struct vmem *vmem, vm_size_t size, int flags)
vm_offset_t addr;
int domain;
KASSERT(vmem == kernel_arena,
("kmem_malloc: Only kernel_arena is supported."));
vm_domainset_iter_malloc_init(&di, kernel_object, &domain, &flags);
do {
addr = kmem_malloc_domain(domain, size, flags);
addr = kmem_malloc_domain(vmem, domain, size, flags);
if (addr != 0)
break;
} while (vm_domainset_iter_malloc(&di, &domain, &flags) == 0);
@ -422,6 +431,7 @@ kmem_back_domain(int domain, vm_object_t object, vm_offset_t addr,
{
vm_offset_t offset, i;
vm_page_t m, mpred;
vm_prot_t prot;
int pflags;
KASSERT(object == kernel_object,
@ -432,6 +442,7 @@ kmem_back_domain(int domain, vm_object_t object, vm_offset_t addr,
pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
if (flags & M_WAITOK)
pflags |= VM_ALLOC_WAITFAIL;
prot = (flags & M_EXEC) != 0 ? VM_PROT_ALL : VM_PROT_RW;
i = 0;
VM_OBJECT_WLOCK(object);
@ -461,8 +472,8 @@ retry:
KASSERT((m->oflags & VPO_UNMANAGED) != 0,
("kmem_malloc: page %p is managed", m));
m->valid = VM_PAGE_BITS_ALL;
pmap_enter(kernel_pmap, addr + i, m, VM_PROT_ALL,
VM_PROT_ALL | PMAP_ENTER_WIRED, 0);
pmap_enter(kernel_pmap, addr + i, m, prot,
prot | PMAP_ENTER_WIRED, 0);
}
VM_OBJECT_WUNLOCK(object);
@ -542,13 +553,28 @@ kmem_unback(vm_object_t object, vm_offset_t addr, vm_size_t size)
void
kmem_free(struct vmem *vmem, vm_offset_t addr, vm_size_t size)
{
struct vmem *arena;
int domain;
#if VM_NRESERVLEVEL > 0
KASSERT(vmem == kernel_arena || vmem == kernel_rwx_arena,
("kmem_free: Only kernel_arena or kernel_rwx_arena are supported."));
#else
KASSERT(vmem == kernel_arena,
("kmem_free: Only kernel_arena is supported."));
#endif
size = round_page(size);
domain = _kmem_unback(kernel_object, addr, size);
vmem_free(vm_dom[domain].vmd_kernel_arena, addr, size);
#if VM_NRESERVLEVEL > 0
if (__predict_true(vmem == kernel_arena))
arena = vm_dom[domain].vmd_kernel_arena;
else
arena = vm_dom[domain].vmd_kernel_rwx_arena;
#else
arena = vm_dom[domain].vmd_kernel_arena;
#endif
vmem_free(arena, addr, size);
}
/*

1
sys/vm/vm_kern.h
View File

@ -70,6 +70,7 @@ extern vm_map_t kernel_map;
extern vm_map_t exec_map;
extern vm_map_t pipe_map;
extern struct vmem *kernel_arena;
extern struct vmem *kernel_rwx_arena;
extern struct vmem *kmem_arena;
extern struct vmem *buffer_arena;
extern struct vmem *transient_arena;

3
sys/vm/vm_pagequeue.h
View File

@ -103,7 +103,8 @@ struct vm_domain {
struct mtx_padalign vmd_free_mtx;
struct mtx_padalign vmd_pageout_mtx;
uma_zone_t vmd_pgcache; /* (c) page free cache. */
struct vmem *vmd_kernel_arena; /* (c) per-domain kva arena. */
struct vmem *vmd_kernel_arena; /* (c) per-domain kva R/W arena. */
struct vmem *vmd_kernel_rwx_arena; /* (c) per-domain kva R/W/X arena. */
u_int vmd_domain; /* (c) Domain number. */
u_int vmd_page_count; /* (c) Total page count. */
long vmd_segs; /* (c) bitmask of the segments */