Hi,
On 9/4/23 20:08, Joel Fernandes (Google) wrote:
It is unsafe to dump vmalloc area information when trying to do so from some contexts. Add a safer trylock version of the same function to do a best-effort VMA finding and use it from vmalloc_dump_obj().
I was a bit confused by the subject which suggests a new function is added, but it seems open-coded in its only caller. I assume it's due to evolution of the series. Something like:
mm/vmalloc: use trylock for vmap_area_lock in vmalloc_dump_obj()
?
I also notice it's trying hard to copy everything from "vm" to temporary variables before unlocking, presumably to prevent use-after-free, so should that be also mentioned in the changelog?
[applied test robot feedback on unused function fix.] [applied Uladzislau feedback on locking.]
Reported-by: Zhen Lei thunder.leizhen@huaweicloud.com Cc: Paul E. McKenney paulmck@kernel.org Cc: rcu@vger.kernel.org Cc: Zqiang qiang.zhang1211@gmail.com Reviewed-by: Uladzislau Rezki (Sony) urezki@gmail.com Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory") Cc: stable@vger.kernel.org Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org
mm/vmalloc.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 93cf99aba335..2c6a0e2ff404 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4274,14 +4274,32 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms) #ifdef CONFIG_PRINTK bool vmalloc_dump_obj(void *object) {
- struct vm_struct *vm; void *objp = (void *)PAGE_ALIGN((unsigned long)object);
- const void *caller;
- struct vm_struct *vm;
- struct vmap_area *va;
- unsigned long addr;
- unsigned int nr_pages;
- vm = find_vm_area(objp);
- if (!vm)
- if (!spin_trylock(&vmap_area_lock))
return false;- va = __find_vmap_area((unsigned long)objp, &vmap_area_root);
- if (!va) {
spin_unlock(&vmap_area_lock);- }
- vm = va->vm;
- if (!vm) {
spin_unlock(&vmap_area_lock);return false;- }
- addr = (unsigned long)vm->addr;
- caller = vm->caller;
- nr_pages = vm->nr_pages;
- spin_unlock(&vmap_area_lock); pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
vm->nr_pages, (unsigned long)vm->addr, vm->caller);
nr_pages, addr, caller);} #endif