Commit 69866e15 authored Apr 06, 2020 by Alexander Potapenko Committed by Linus Torvalds Apr 07, 2020

lib/stackdepot.c: check depot_index before accessing the stack slab

Avoid crashes on corrupted stack ids.  Despite stack ID corruption may
indicate other bugs in the program, we'd better fail gracefully on such
IDs instead of crashing the kernel.

This patch has been previously mailed as part of KMSAN RFC patch series.

Link: http://lkml.kernel.org/r/20200220141916.55455-1-glider@google.com


Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
From: Dan Carpenter <dan.carpenter@oracle.com>
Subject: lib/stackdepot.c: fix a condition in stack_depot_fetch()

We should check for a NULL pointer first before adding the offset.
Otherwise if the pointer is NULL and the offset is non-zero, it will lead
to an Oops.

Fixes: d45048e65a59 ("lib/stackdepot.c: check depot_index before accessing the stack slab")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Alexander Potapenko <glider@google.com>
Link: http://lkml.kernel.org/r/20200312113006.GA20562@mwanda


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 9cf016e6

lib/stackdepot.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -202,9 +202,20 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
		unsigned long **entries)
		{
		union handle_parts parts = { .handle = handle };
		void *slab = stack_slabs[parts.slabindex];
		void *slab;
		size_t offset = parts.offset << STACK_ALLOC_ALIGN;
		struct stack_record *stack = slab + offset;
		struct stack_record *stack;

		*entries = NULL;
		if (parts.slabindex > depot_index) {
		WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
		parts.slabindex, depot_index, handle);
		return 0;
		}
		slab = stack_slabs[parts.slabindex];
		if (!slab)
		return 0;
		stack = slab + offset;

		*entries = stack->entries;
		return stack->size;

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