Messages in this thread | | | Subject | Re: [RFC PATCH 1/2] lib, stackdepot: check stackdepot handle before accessing slabs. | From | imran.f.khan@oracle ... | Date | Thu, 2 Sep 2021 10:12:58 +1000 |
| |
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@oracle.com> >> Suggested-by: Vlastimil Babka <vbabka@suse.cz> > > 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
| |