docs:mm: fixed spelling and grammar mistakes on vmalloc kernel stack page

Signed-off-by: Dennis Lam <dennis.lamerice@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20240906204914.42698-2-dennis.lamerice@gmail.com>

Author: Dennis Lam

Documentation/mm/vmalloced-kernel-stacks.rst

@@ -110,7 +110,7 @@ Bulk of the code is in:
 `kernel/fork.c <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/fork.c>`.
 
 stack_vm_area pointer in task_struct keeps track of the virtually allocated
-stack and a non-null stack_vm_area pointer serves as a indication that the
+stack and a non-null stack_vm_area pointer serves as an indication that the
 virtually mapped kernel stacks are enabled.
 
 ::
@@ -120,8 +120,8 @@ virtually mapped kernel stacks are enabled.
 Stack overflow handling
 -----------------------
 
-Leading and trailing guard pages help detect stack overflows. When stack
-overflows into the guard pages, handlers have to be careful not overflow
+Leading and trailing guard pages help detect stack overflows. When the stack
+overflows into the guard pages, handlers have to be careful not to overflow
 the stack again. When handlers are called, it is likely that very little
 stack space is left.
 
@@ -148,6 +148,6 @@ Conclusions
 - THREAD_INFO_IN_TASK gets rid of arch-specific thread_info entirely and
   simply embed the thread_info (containing only flags) and 'int cpu' into
   task_struct.
-- The thread stack can be free'ed as soon as the task is dead (without
+- The thread stack can be freed as soon as the task is dead (without
   waiting for RCU) and then, if vmapped stacks are in use, cache the
   entire stack for reuse on the same cpu.