[PATCH] of: fix kmemleak crash caused by imbalance in early memory reservation

[Mike Rapoport]

Marc Gonzalez reported the following kmemleak crash:

Unable to handle kernel paging request at virtual address ffffffc021e00000
Mem abort info:
  ESR = 0x96000006
  Exception class = DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
Data abort info:
  ISV = 0, ISS = 0x00000006
  CM = 0, WnR = 0
swapper pgtable: 4k pages, 39-bit VAs, pgdp = (____ptrval____)
[ffffffc021e00000] pgd=000000017e3ba803, pud=000000017e3ba803,
pmd=0000000000000000
Internal error: Oops: 96000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 6 PID: 523 Comm: kmemleak Tainted: G S      W         5.0.0-rc1 #13
Hardware name: Qualcomm Technologies, Inc. MSM8998 v1 MTP (DT)
pstate: 80000085 (Nzcv daIf -PAN -UAO)
pc : scan_block+0x70/0x190
lr : scan_block+0x6c/0x190
sp : ffffff8012e8bd20
x29: ffffff8012e8bd20 x28: ffffffc0fdbaf018
x27: ffffffc022000000 x26: 0000000000000080
x25: ffffff8011aadf70 x24: ffffffc0f8cc8000
x23: ffffff8010dc8000 x22: ffffff8010dc8830
x21: ffffffc021e00ff9 x20: ffffffc0f8cc8050
x19: ffffffc021e00000 x18: 0000000000002409
x17: 0000000000000200 x16: 0000000000000000
x15: ffffff8010e14dd8 x14: 0000000000002406
x13: 000000004c4dd0c6 x12: ffffffc0f77dad58
x11: 0000000000000001 x10: ffffff8010d9e688
x9 : ffffff8010d9f000 x8 : ffffff8010d9e688
x7 : 0000000000000002 x6 : 0000000000000000
x5 : ffffff8011511c20 x4 : 00000000000026d1
x3 : ffffff8010e14d88 x2 : 5b36396f4e7d4000
x1 : 0000000000208040 x0 : 0000000000000000
Process kmemleak (pid: 523, stack limit = 0x(____ptrval____))
Call trace:
 scan_block+0x70/0x190
 scan_gray_list+0x108/0x1c0
 kmemleak_scan+0x33c/0x7c0
 kmemleak_scan_thread+0x98/0xf0
 kthread+0x11c/0x120
 ret_from_fork+0x10/0x1c
Code: f9000fb4 d503201f 97ffffd2 35000580 (f9400260)
---[ end trace 176d6ed9d86a0c33 ]---
note: kmemleak[523] exited with preempt_count 2

The crash happens when a no-map area is allocated in
early_init_dt_alloc_reserved_memory_arch(). The allocated region is
registered with kmemleak, but it is then removed from memblock using
memblock_remove() that is not kmemleak-aware.

Replacing __memblock_alloc_base() with memblock_find_in_range() makes sure
that the allocated memory is not added to kmemleak and then
memblock_remove()'ing this memory is safe.

As a bonus, since memblock_find_in_range() ensures the allocation in the
specified range, the bounds check can be removed.

Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Tested-by: Marc Gonzalez <marc.w.gonzalez@xxxxxxx>
---
 drivers/of/of_reserved_mem.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 1977ee0adcb1..6807a1cffe55 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -37,21 +37,16 @@ int __init __weak early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
 	 */
 	end = !end ? MEMBLOCK_ALLOC_ANYWHERE : end;
 	align = !align ? SMP_CACHE_BYTES : align;
-	base = __memblock_alloc_base(size, align, end);
+	base = memblock_find_in_range(size, align, start, end);
 	if (!base)
 		return -ENOMEM;
 
-	/*
-	 * Check if the allocated region fits in to start..end window
-	 */
-	if (base < start) {
-		memblock_free(base, size);
-		return -ENOMEM;
-	}
-
 	*res_base = base;
 	if (nomap)
 		return memblock_remove(base, size);
+	else
+		return memblock_reserve(base, size);
+
 	return 0;
 }
 
-- 
2.7.4