Change flex_array_prealloc to take the number of elements for which space
should be allocated instead of the last (inclusive) element. Users
and documentation are updated accordingly.
Based-on-patch-by: Steffen Klassert <[email protected]>
Signed-off-by: Eric Paris <[email protected]>
---
Documentation/flexible-arrays.txt | 4 ++--
include/linux/flex_array.h | 2 +-
lib/flex_array.c | 13 ++++++++-----
security/selinux/ss/policydb.c | 6 +++---
4 files changed, 14 insertions(+), 11 deletions(-)
diff --git a/Documentation/flexible-arrays.txt b/Documentation/flexible-arrays.txt
index cb8a3a0..df904ae 100644
--- a/Documentation/flexible-arrays.txt
+++ b/Documentation/flexible-arrays.txt
@@ -66,10 +66,10 @@ trick is to ensure that any needed memory allocations are done before
entering atomic context, using:
int flex_array_prealloc(struct flex_array *array, unsigned int start,
- unsigned int end, gfp_t flags);
+ unsigned int nr_elements, gfp_t flags);
This function will ensure that memory for the elements indexed in the range
-defined by start and end has been allocated. Thereafter, a
+defined by start and nr_elements has been allocated. Thereafter, a
flex_array_put() call on an element in that range is guaranteed not to
block.
diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h
index 70e4efa..ebeb2f3 100644
--- a/include/linux/flex_array.h
+++ b/include/linux/flex_array.h
@@ -61,7 +61,7 @@ struct flex_array {
struct flex_array *flex_array_alloc(int element_size, unsigned int total,
gfp_t flags);
int flex_array_prealloc(struct flex_array *fa, unsigned int start,
- unsigned int end, gfp_t flags);
+ unsigned int nr_elements, gfp_t flags);
void flex_array_free(struct flex_array *fa);
void flex_array_free_parts(struct flex_array *fa);
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
diff --git a/lib/flex_array.c b/lib/flex_array.c
index c0ea40b..0c33b24 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -232,10 +232,10 @@ EXPORT_SYMBOL(flex_array_clear);
/**
* flex_array_prealloc - guarantee that array space exists
- * @fa: the flex array for which to preallocate parts
- * @start: index of first array element for which space is allocated
- * @end: index of last (inclusive) element for which space is allocated
- * @flags: page allocation flags
+ * @fa: the flex array for which to preallocate parts
+ * @start: index of first array element for which space is allocated
+ * @nr_elements: number of elements for which space is allocated
+ * @flags: page allocation flags
*
* This will guarantee that no future calls to flex_array_put()
* will allocate memory. It can be used if you are expecting to
@@ -245,13 +245,16 @@ EXPORT_SYMBOL(flex_array_clear);
* Locking must be provided by the caller.
*/
int flex_array_prealloc(struct flex_array *fa, unsigned int start,
- unsigned int end, gfp_t flags)
+ unsigned int nr_elements, gfp_t flags)
{
int start_part;
int end_part;
int part_nr;
+ unsigned int end;
struct flex_array_part *part;
+ end = start + nr_elements - 1;
+
if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
return -ENOSPC;
if (elements_fit_in_base(fa))
diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 3258799..1b150d7 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -551,7 +551,7 @@ static int policydb_index(struct policydb *p)
goto out;
rc = flex_array_prealloc(p->type_val_to_struct_array, 0,
- p->p_types.nprim - 1, GFP_KERNEL | __GFP_ZERO);
+ p->p_types.nprim, GFP_KERNEL | __GFP_ZERO);
if (rc)
goto out;
@@ -568,7 +568,7 @@ static int policydb_index(struct policydb *p)
goto out;
rc = flex_array_prealloc(p->sym_val_to_name[i],
- 0, p->symtab[i].nprim - 1,
+ 0, p->symtab[i].nprim,
GFP_KERNEL | __GFP_ZERO);
if (rc)
goto out;
@@ -2445,7 +2445,7 @@ int policydb_read(struct policydb *p, void *fp)
goto bad;
/* preallocate so we don't have to worry about the put ever failing */
- rc = flex_array_prealloc(p->type_attr_map_array, 0, p->p_types.nprim - 1,
+ rc = flex_array_prealloc(p->type_attr_map_array, 0, p->p_types.nprim,
GFP_KERNEL | __GFP_ZERO);
if (rc)
goto bad;
Just like kmalloc will allow one to allocate a 0 length segment of memory
flex arrays should do the same thing. It should bomb if you try to use
something, but it should at least allow the allocation.
Based-on-patch-by: Steffen Klassert <[email protected]>
Signed-off-by: Eric Paris <[email protected]>
---
lib/flex_array.c | 11 ++++++++++-
1 files changed, 10 insertions(+), 1 deletions(-)
diff --git a/lib/flex_array.c b/lib/flex_array.c
index 0c33b24..2554a5f 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -253,9 +253,16 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
unsigned int end;
struct flex_array_part *part;
+ if (!fa->total_nr_elements && !start)
+ return 0;
+ if (start >= fa->total_nr_elements)
+ return -ENOSPC;
+ if (!nr_elements)
+ return 0;
+
end = start + nr_elements - 1;
- if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
+ if (end >= fa->total_nr_elements)
return -ENOSPC;
if (elements_fit_in_base(fa))
return 0;
@@ -346,6 +353,8 @@ int flex_array_shrink(struct flex_array *fa)
int part_nr;
int ret = 0;
+ if (!fa->total_nr_elements)
+ return 0;
if (elements_fit_in_base(fa))
return ret;
for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {
allow elements of 0 length. We already allow flex_arrays with 0 elements, but
this patch allow us to have elements that are 0 bytes long.
Based-on-patch-by: Steffen Klassert <[email protected]>
Signed-off-by: Eric Paris <[email protected]>
---
lib/flex_array.c | 26 ++++++++++++++++++++------
1 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/lib/flex_array.c b/lib/flex_array.c
index 2554a5f..dcd91d5 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -88,8 +88,11 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total,
gfp_t flags)
{
struct flex_array *ret;
- int max_size = FLEX_ARRAY_NR_BASE_PTRS *
- FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
+ int max_size = 0;
+
+ if (element_size)
+ max_size = FLEX_ARRAY_NR_BASE_PTRS *
+ FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
/* max_size will end up 0 if element_size > PAGE_SIZE */
if (total > max_size)
@@ -183,15 +186,18 @@ __fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
gfp_t flags)
{
- int part_nr = fa_element_to_part_nr(fa, element_nr);
+ int part_nr;
struct flex_array_part *part;
void *dst;
if (element_nr >= fa->total_nr_elements)
return -ENOSPC;
+ if (!fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
part = (struct flex_array_part *)&fa->parts[0];
else {
+ part_nr = fa_element_to_part_nr(fa, element_nr);
part = __fa_get_part(fa, part_nr, flags);
if (!part)
return -ENOMEM;
@@ -211,15 +217,18 @@ EXPORT_SYMBOL(flex_array_put);
*/
int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
{
- int part_nr = fa_element_to_part_nr(fa, element_nr);
+ int part_nr;
struct flex_array_part *part;
void *dst;
if (element_nr >= fa->total_nr_elements)
return -ENOSPC;
+ if (!fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
part = (struct flex_array_part *)&fa->parts[0];
else {
+ part_nr = fa_element_to_part_nr(fa, element_nr);
part = fa->parts[part_nr];
if (!part)
return -EINVAL;
@@ -264,6 +273,8 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
if (end >= fa->total_nr_elements)
return -ENOSPC;
+ if (!fa->element_size)
+ return 0;
if (elements_fit_in_base(fa))
return 0;
start_part = fa_element_to_part_nr(fa, start);
@@ -291,14 +302,17 @@ EXPORT_SYMBOL(flex_array_prealloc);
*/
void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
{
- int part_nr = fa_element_to_part_nr(fa, element_nr);
+ int part_nr;
struct flex_array_part *part;
+ if (!fa->element_size)
+ return NULL;
if (element_nr >= fa->total_nr_elements)
return NULL;
if (elements_fit_in_base(fa))
part = (struct flex_array_part *)&fa->parts[0];
else {
+ part_nr = fa_element_to_part_nr(fa, element_nr);
part = fa->parts[part_nr];
if (!part)
return NULL;
@@ -353,7 +367,7 @@ int flex_array_shrink(struct flex_array *fa)
int part_nr;
int ret = 0;
- if (!fa->total_nr_elements)
+ if (!fa->total_nr_elements || !fa->element_size)
return 0;
if (elements_fit_in_base(fa))
return ret;
On Mon, 25 Apr 2011 21:45:31 -0400
Eric Paris <[email protected]> wrote:
> Change flex_array_prealloc to take the number of elements for which space
> should be allocated instead of the last (inclusive) element. Users
> and documentation are updated accordingly.
Why?
On Mon, 25 Apr 2011 21:45:37 -0400
Eric Paris <[email protected]> wrote:
> Just like kmalloc will allow one to allocate a 0 length segment of memory
> flex arrays should do the same thing. It should bomb if you try to use
> something, but it should at least allow the allocation.
Well I suppose that's vaguely sensible, but it adds additional code for
no apparent benefit.
IOW: why?
On Mon, 25 Apr 2011 21:45:43 -0400
Eric Paris <[email protected]> wrote:
> allow elements of 0 length. We already allow flex_arrays with 0 elements, but
> this patch allow us to have elements that are 0 bytes long.
Again, sounds vaguely useful but it adds code and churns the code for
no apparent benefit.
IOW2: why?
On Tue, 2011-04-26 at 11:56 -0700, Andrew Morton wrote:
> On Mon, 25 Apr 2011 21:45:31 -0400
> Eric Paris <[email protected]> wrote:
>
> > Change flex_array_prealloc to take the number of elements for which space
> > should be allocated instead of the last (inclusive) element. Users
> > and documentation are updated accordingly.
>
> Why?
All three of these patches came from these discussions:
http://marc.info/?t=129552800100005&r=1&w=2
http://marc.info/?t=129646395700004&r=1&w=2
http://marc.info/?t=129708178200007&r=1&w=2
1/3 was changed just because it seemed to be the way the interface was
used
2/3 was changed because the 2.6.38 kernel fails to load certain selinux
policies which worked under 2.6.37 because of this lack of functionality
3/3 was changed just because that's how maybe it should work, although
there are no known users.
I can certainly update 2/3 to better explain the rational but I can't
really do any better on 1/3 and 3/3 other than to just say what the
change is......
-Eric
On Mon, 2011-04-25 at 21:45 -0400, Eric Paris wrote:
> Change flex_array_prealloc to take the number of elements for which space
> should be allocated instead of the last (inclusive) element. Users
> and documentation are updated accordingly.
>
> Based-on-patch-by: Steffen Klassert <[email protected]>
> Signed-off-by: Eric Paris <[email protected]>
Perhaps add this to the description?
flex_arrays got introduced before they had users. When folks started
using it, they ended up needing a different API than we coded up
originally. This swaps over to the API that folks apparently need.
Acked-by: Dave Hansen <[email protected]>
-- Dave
On Mon, 2011-04-25 at 21:45 -0400, Eric Paris wrote:
> Just like kmalloc will allow one to allocate a 0 length segment of memory
> flex arrays should do the same thing. It should bomb if you try to use
> something, but it should at least allow the allocation.
>
> Based-on-patch-by: Steffen Klassert <[email protected]>
> Signed-off-by: Eric Paris <[email protected]>
> ---
>
> lib/flex_array.c | 11 ++++++++++-
> 1 files changed, 10 insertions(+), 1 deletions(-)
>
> diff --git a/lib/flex_array.c b/lib/flex_array.c
> index 0c33b24..2554a5f 100644
> --- a/lib/flex_array.c
> +++ b/lib/flex_array.c
> @@ -253,9 +253,16 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
> unsigned int end;
> struct flex_array_part *part;
>
> + if (!fa->total_nr_elements && !start)
> + return 0;
I guess it works either way, but I'd say that checking for a zero 'len'
prealloc would be more important (and meaningful) than checking a zero
'start'.
If someone passed start=0 and len=44 for a fa->total_nr_elements=0
array, I'd expect -ENOSPC, but this would return 0.
-- Dave
On Tue, 2011-04-26 at 13:38 -0700, Dave Hansen wrote:
> On Mon, 2011-04-25 at 21:45 -0400, Eric Paris wrote:
> > Just like kmalloc will allow one to allocate a 0 length segment of memory
> > flex arrays should do the same thing. It should bomb if you try to use
> > something, but it should at least allow the allocation.
> >
> > Based-on-patch-by: Steffen Klassert <[email protected]>
> > Signed-off-by: Eric Paris <[email protected]>
> > ---
> >
> > lib/flex_array.c | 11 ++++++++++-
> > 1 files changed, 10 insertions(+), 1 deletions(-)
> >
> > diff --git a/lib/flex_array.c b/lib/flex_array.c
> > index 0c33b24..2554a5f 100644
> > --- a/lib/flex_array.c
> > +++ b/lib/flex_array.c
> > @@ -253,9 +253,16 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
> > unsigned int end;
> > struct flex_array_part *part;
> >
> > + if (!fa->total_nr_elements && !start)
> > + return 0;
>
> I guess it works either way, but I'd say that checking for a zero 'len'
> prealloc would be more important (and meaningful) than checking a zero
> 'start'.
>
> If someone passed start=0 and len=44 for a fa->total_nr_elements=0
> array, I'd expect -ENOSPC, but this would return 0.
will fix.
if (!nr_elements && !start)
return 0;
-Eric
>
> -- Dave
>
On Mon, 2011-04-25 at 21:45 -0400, Eric Paris wrote:
> allow elements of 0 length. We already allow flex_arrays with 0
> elements, but
> this patch allow us to have elements that are 0 bytes long.
>
> Based-on-patch-by: Steffen Klassert <[email protected]>
> Signed-off-by: Eric Paris <[email protected]>
I'd like to see a bit of the history in the changelog. kmalloc(0)
returns NULL, and we'd effectively like to do the same since flex_arrays
really are like a mini allocator. The 0-sized elements come from
userspace and we *have* to handle them in the security code, etc...
The code looks good, though.
Acked-by: Dave Hansen <[email protected]>
-- Dave