On 4/27/20 12:10 PM, Christopher Lameter wrote:
On Mon, 27 Apr 2020, Waiman Long wrote:
To fix it, use the check "s->offset == s->inuse" in the new helper
function freeptr_after_object() instead. Also add another helper function
get_info_end() to return the end of info block (inuse + free pointer
if not overlapping with object).
Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
mm/slub.c | 37 ++++++++++++++++++++++---------------
1 file changed, 22 insertions(+), 15 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 0e736d66bb42..68f1b4b1c309 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -551,15 +551,29 @@ static void print_section(char *level, char *text, u8 *addr,
metadata_access_disable();
}
+static inline bool freeptr_after_object(struct kmem_cache *s)
bool freeptr_outside_of_object()?
I can change to that name. It doesn't really matter to me.
+{
+ return s->offset == s->inuse;
s->offset >= s->inuse?
There may be a redzone after the object.
Technically inuse is object + red zone. According to calculate_sizes():
s->inuse = size;
if (((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
s->ctor)) {
/*
* Relocate free pointer after the object if it is not
* permitted to overwrite the first word of the object on
* kmem_cache_free.
*
* This is the case if we do RCU, have a constructor or
* destructor or are poisoning the objects.
*/
s->offset = size;
size += sizeof(void *);
So (s->offset == s->inuse) when the free pointer is outside of the object.
+static inline unsigned int get_info_end(struct kmem_cache *s)
static inline track_offset()?
The main reason why I don't use that is because there is a track data
structure in slub. There are functions name get_track() and set_track().
I don't want to confuse with them.
Cheers,
Longman
