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xen/xenbus: avoid large structs and arrays on the stack
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xenbus_map_ring_valloc() and its sub-functions are putting quite large
structs and arrays on the stack. This is problematic at runtime, but
might also result in build failures (e.g. with clang due to the option
-Werror,-Wframe-larger-than=... used).

Fix that by moving most of the data from the stack into a dynamically
allocated struct. Performance is no issue here, as
xenbus_map_ring_valloc() is used only when adding a new PV device to
a backend driver.

While at it move some duplicated code from pv/hvm specific mapping
functions to the single caller.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200701121638.19840-2-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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@jgross1
jgross1 authored and Boris Ostrovsky committed Jul 2, 2020
1 parent caef73c commit 3848e4e
Showing 1 changed file with 83 additions and 78 deletions.
161 changes: 83 additions & 78 deletions drivers/xen/xenbus/xenbus_client.c
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Original file line number Diff line number Diff line change
Expand Up @@ -69,11 +69,27 @@ struct xenbus_map_node {
unsigned int nr_handles;
};

struct map_ring_valloc {
struct xenbus_map_node *node;

/* Why do we need two arrays? See comment of __xenbus_map_ring */
union {
unsigned long addrs[XENBUS_MAX_RING_GRANTS];
pte_t *ptes[XENBUS_MAX_RING_GRANTS];
};
phys_addr_t phys_addrs[XENBUS_MAX_RING_GRANTS];

struct gnttab_map_grant_ref map[XENBUS_MAX_RING_GRANTS];
struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];

unsigned int idx; /* HVM only. */
};

static DEFINE_SPINLOCK(xenbus_valloc_lock);
static LIST_HEAD(xenbus_valloc_pages);

struct xenbus_ring_ops {
int (*map)(struct xenbus_device *dev,
int (*map)(struct xenbus_device *dev, struct map_ring_valloc *info,
grant_ref_t *gnt_refs, unsigned int nr_grefs,
void **vaddr);
int (*unmap)(struct xenbus_device *dev, void *vaddr);
Expand Down Expand Up @@ -449,12 +465,32 @@ int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
unsigned int nr_grefs, void **vaddr)
{
int err;
struct map_ring_valloc *info;

*vaddr = NULL;

if (nr_grefs > XENBUS_MAX_RING_GRANTS)
return -EINVAL;

info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info)
return -ENOMEM;

info->node = kzalloc(sizeof(*info->node), GFP_KERNEL);
if (!info->node) {
err = -ENOMEM;
goto out;
}

err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);

err = ring_ops->map(dev, gnt_refs, nr_grefs, vaddr);
/* Some hypervisors are buggy and can return 1. */
if (err > 0)
err = GNTST_general_error;

out:
kfree(info->node);
kfree(info);
return err;
}
EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
Expand All @@ -466,56 +502,53 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
grant_ref_t *gnt_refs,
unsigned int nr_grefs,
grant_handle_t *handles,
phys_addr_t *addrs,
struct map_ring_valloc *info,
unsigned int flags,
bool *leaked)
{
struct gnttab_map_grant_ref map[XENBUS_MAX_RING_GRANTS];
struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
int i, j;
int err = GNTST_okay;

if (nr_grefs > XENBUS_MAX_RING_GRANTS)
return -EINVAL;

for (i = 0; i < nr_grefs; i++) {
memset(&map[i], 0, sizeof(map[i]));
gnttab_set_map_op(&map[i], addrs[i], flags, gnt_refs[i],
dev->otherend_id);
gnttab_set_map_op(&info->map[i], info->phys_addrs[i], flags,
gnt_refs[i], dev->otherend_id);
handles[i] = INVALID_GRANT_HANDLE;
}

gnttab_batch_map(map, i);
gnttab_batch_map(info->map, i);

for (i = 0; i < nr_grefs; i++) {
if (map[i].status != GNTST_okay) {
err = map[i].status;
xenbus_dev_fatal(dev, map[i].status,
if (info->map[i].status != GNTST_okay) {
err = info->map[i].status;
xenbus_dev_fatal(dev, info->map[i].status,
"mapping in shared page %d from domain %d",
gnt_refs[i], dev->otherend_id);
goto fail;
} else
handles[i] = map[i].handle;
handles[i] = info->map[i].handle;
}

return GNTST_okay;

fail:
for (i = j = 0; i < nr_grefs; i++) {
if (handles[i] != INVALID_GRANT_HANDLE) {
memset(&unmap[j], 0, sizeof(unmap[j]));
gnttab_set_unmap_op(&unmap[j], (phys_addr_t)addrs[i],
gnttab_set_unmap_op(&info->unmap[j],
info->phys_addrs[i],
GNTMAP_host_map, handles[i]);
j++;
}
}

if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, j))
if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j))
BUG();

*leaked = false;
for (i = 0; i < j; i++) {
if (unmap[i].status != GNTST_okay) {
if (info->unmap[i].status != GNTST_okay) {
*leaked = true;
break;
}
Expand Down Expand Up @@ -566,21 +599,12 @@ static int xenbus_unmap_ring(struct xenbus_device *dev, grant_handle_t *handles,
return err;
}

struct map_ring_valloc_hvm
{
unsigned int idx;

/* Why do we need two arrays? See comment of __xenbus_map_ring */
phys_addr_t phys_addrs[XENBUS_MAX_RING_GRANTS];
unsigned long addrs[XENBUS_MAX_RING_GRANTS];
};

static void xenbus_map_ring_setup_grant_hvm(unsigned long gfn,
unsigned int goffset,
unsigned int len,
void *data)
{
struct map_ring_valloc_hvm *info = data;
struct map_ring_valloc *info = data;
unsigned long vaddr = (unsigned long)gfn_to_virt(gfn);

info->phys_addrs[info->idx] = vaddr;
Expand All @@ -589,39 +613,28 @@ static void xenbus_map_ring_setup_grant_hvm(unsigned long gfn,
info->idx++;
}

static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
grant_ref_t *gnt_ref,
unsigned int nr_grefs,
void **vaddr)
static int xenbus_map_ring_hvm(struct xenbus_device *dev,
struct map_ring_valloc *info,
grant_ref_t *gnt_ref,
unsigned int nr_grefs,
void **vaddr)
{
struct xenbus_map_node *node;
struct xenbus_map_node *node = info->node;
int err;
void *addr;
bool leaked = false;
struct map_ring_valloc_hvm info = {
.idx = 0,
};
unsigned int nr_pages = XENBUS_PAGES(nr_grefs);

if (nr_grefs > XENBUS_MAX_RING_GRANTS)
return -EINVAL;

*vaddr = NULL;

node = kzalloc(sizeof(*node), GFP_KERNEL);
if (!node)
return -ENOMEM;

err = alloc_xenballooned_pages(nr_pages, node->hvm.pages);
if (err)
goto out_err;

gnttab_foreach_grant(node->hvm.pages, nr_grefs,
xenbus_map_ring_setup_grant_hvm,
&info);
info);

err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
info.phys_addrs, GNTMAP_host_map, &leaked);
info, GNTMAP_host_map, &leaked);
node->nr_handles = nr_grefs;

if (err)
Expand All @@ -641,19 +654,20 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
spin_unlock(&xenbus_valloc_lock);

*vaddr = addr;
info->node = NULL;

return 0;

out_xenbus_unmap_ring:
if (!leaked)
xenbus_unmap_ring(dev, node->handles, nr_grefs, info.addrs);
xenbus_unmap_ring(dev, node->handles, nr_grefs, info->addrs);
else
pr_alert("leaking %p size %u page(s)",
addr, nr_pages);
out_free_ballooned_pages:
if (!leaked)
free_xenballooned_pages(nr_pages, node->hvm.pages);
out_err:
kfree(node);
return err;
}

Expand All @@ -676,40 +690,30 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);

#ifdef CONFIG_XEN_PV
static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
grant_ref_t *gnt_refs,
unsigned int nr_grefs,
void **vaddr)
static int xenbus_map_ring_pv(struct xenbus_device *dev,
struct map_ring_valloc *info,
grant_ref_t *gnt_refs,
unsigned int nr_grefs,
void **vaddr)
{
struct xenbus_map_node *node;
struct xenbus_map_node *node = info->node;
struct vm_struct *area;
pte_t *ptes[XENBUS_MAX_RING_GRANTS];
phys_addr_t phys_addrs[XENBUS_MAX_RING_GRANTS];
int err = GNTST_okay;
int i;
bool leaked;

*vaddr = NULL;

if (nr_grefs > XENBUS_MAX_RING_GRANTS)
return -EINVAL;

node = kzalloc(sizeof(*node), GFP_KERNEL);
if (!node)
return -ENOMEM;

area = alloc_vm_area(XEN_PAGE_SIZE * nr_grefs, ptes);
area = alloc_vm_area(XEN_PAGE_SIZE * nr_grefs, info->ptes);
if (!area) {
kfree(node);
return -ENOMEM;
}

for (i = 0; i < nr_grefs; i++)
phys_addrs[i] = arbitrary_virt_to_machine(ptes[i]).maddr;
info->phys_addrs[i] =
arbitrary_virt_to_machine(info->ptes[i]).maddr;

err = __xenbus_map_ring(dev, gnt_refs, nr_grefs, node->handles,
phys_addrs,
GNTMAP_host_map | GNTMAP_contains_pte,
info, GNTMAP_host_map | GNTMAP_contains_pte,
&leaked);
if (err)
goto failed;
Expand All @@ -722,6 +726,8 @@ static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
spin_unlock(&xenbus_valloc_lock);

*vaddr = area->addr;
info->node = NULL;

return 0;

failed:
Expand All @@ -730,11 +736,10 @@ static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
else
pr_alert("leaking VM area %p size %u page(s)", area, nr_grefs);

kfree(node);
return err;
}

static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
static int xenbus_unmap_ring_pv(struct xenbus_device *dev, void *vaddr)
{
struct xenbus_map_node *node;
struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
Expand Down Expand Up @@ -798,12 +803,12 @@ static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
}

static const struct xenbus_ring_ops ring_ops_pv = {
.map = xenbus_map_ring_valloc_pv,
.unmap = xenbus_unmap_ring_vfree_pv,
.map = xenbus_map_ring_pv,
.unmap = xenbus_unmap_ring_pv,
};
#endif

struct unmap_ring_vfree_hvm
struct unmap_ring_hvm
{
unsigned int idx;
unsigned long addrs[XENBUS_MAX_RING_GRANTS];
Expand All @@ -814,19 +819,19 @@ static void xenbus_unmap_ring_setup_grant_hvm(unsigned long gfn,
unsigned int len,
void *data)
{
struct unmap_ring_vfree_hvm *info = data;
struct unmap_ring_hvm *info = data;

info->addrs[info->idx] = (unsigned long)gfn_to_virt(gfn);

info->idx++;
}

static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
static int xenbus_unmap_ring_hvm(struct xenbus_device *dev, void *vaddr)
{
int rv;
struct xenbus_map_node *node;
void *addr;
struct unmap_ring_vfree_hvm info = {
struct unmap_ring_hvm info = {
.idx = 0,
};
unsigned int nr_pages;
Expand Down Expand Up @@ -887,8 +892,8 @@ enum xenbus_state xenbus_read_driver_state(const char *path)
EXPORT_SYMBOL_GPL(xenbus_read_driver_state);

static const struct xenbus_ring_ops ring_ops_hvm = {
.map = xenbus_map_ring_valloc_hvm,
.unmap = xenbus_unmap_ring_vfree_hvm,
.map = xenbus_map_ring_hvm,
.unmap = xenbus_unmap_ring_hvm,
};

void __init xenbus_ring_ops_init(void)
Expand Down

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