On 1/9/21 6:58 pm, Vlastimil Babka wrote:
+CC linux-mm, Alex
On 9/1/21 07:19, Imran Khan wrote:
stack_depot_save allocates slabs that will be used for storing
objects in future.If this slab allocation fails we may get to
a situation where space allocation for a new stack_record fails,
causing stack_depot_save to return 0 as handle.
If user of this handle ends up invoking stack_depot_fetch with
this handle value, current implementation of stack_depot_fetch
will end up using slab from wrong index.
To avoid this check handle value at the beginning.
Also issue a warning for nil handle values and when slab allocation
for stackdepot fails for the first time.
Signed-off-by: Imran Khan <imran.f.khan@xxxxxxxxxx>
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Agree but without the warnings please, especially the "stack depot handle is
absent" one. It's just something that can happen e.g. in GFP_NOWAIT contexts
and no need to spam dmesg.
Okay. I have removed warnings in v2 of patch set.
---
lib/stackdepot.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 0a2e417f83cb..1d42ef9ef766 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -232,6 +232,10 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
struct stack_record *stack;
*entries = NULL;
+ if (!handle) {
+ WARN(1, "stack depot handle is absent.\n");
+ return 0;
+ }
if (parts.slabindex > depot_index) {
WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
parts.slabindex, depot_index, handle);
@@ -303,6 +307,8 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
if (page)
prealloc = page_address(page);
+ else
+ WARN_ONCE(1, "slab allocation for stack depot failed.\n");
}
raw_spin_lock_irqsave(&depot_lock, flags);
Thanks for reviewing this.
--Imran
