[PATCH 4.9 04/26] staging: android: ion: fix page is NULL

Greg Kroah-Hartman
2021-09-24T12:46:39Z

From: Cheng Chao <cs.os.kernel@gmail.com>

Fixes: commit e7f63771b60e ("ION: Sys_heap: Add cached pool to spead up cached buffer alloc")
the commit e7f63771b60e introduced the bug which didn't test page which maybe NULL.
and previous logic was right.

the e7f63771b60e has been merged in v4.8-rc3, only longterm 4.9.x has this bug,
and other longterm/stable version have not.

kernel panic is here when page is NULL:

Unable to handle kernel paging request at virtual address b0380000
pgd = d9d94000
[b0380000] *pgd=00000000
Internal error: Oops: 2805 [#1] PREEMPT SMP ARM
...
task: daa2dd00 task.stack: da194000
PC is at v7_dma_clean_range+0x1c/0x34
LR is at arm_dma_sync_single_for_device+0x44/0x58
pc : [<c011aa0c>] lr : [<c011645c>] psr: 200f0013
sp : da195da0 ip : dc1f9000 fp : c1043dc4
r10: 00000000 r9 : c16f1f58 r8 : 00000001
r7 : c1621f94 r6 : c0116418 r5 : 00000000 r4 : c011aa58
r3 : 0000003f r2 : 00000040 r1 : b0480000 r0 : b0380000
Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
Control: 10c5383d Table: 19d9406a DAC: 00000051
...
[<c011aa0c>] (v7_dma_clean_range) from [<c011645c>] (arm_dma_sync_single_for_device+0x44/0x58)
[<c011645c>] (arm_dma_sync_single_for_device) from [<c0117088>] (arm_dma_sync_sg_for_device+0x50/0x7c)
[<c0117088>] (arm_dma_sync_sg_for_device) from [<c0c033c4>] (ion_pages_sync_for_device+0xb0/0xec)
[<c0c033c4>] (ion_pages_sync_for_device) from [<c0c054ac>] (ion_system_heap_allocate+0x2a0/0x2e0)
[<c0c054ac>] (ion_system_heap_allocate) from [<c0c02c78>] (ion_alloc+0x12c/0x494)
[<c0c02c78>] (ion_alloc) from [<c0c03eac>] (ion_ioctl+0x510/0x63c)
[<c0c03eac>] (ion_ioctl) from [<c027c4b0>] (do_vfs_ioctl+0xa8/0x9b4)
[<c027c4b0>] (do_vfs_ioctl) from [<c027ce28>] (SyS_ioctl+0x6c/0x7c)
[<c027ce28>] (SyS_ioctl) from [<c0108a40>] (ret_fast_syscall+0x0/0x48)
Code: e3a02004 e1a02312 e2423001 e1c00003 (ee070f3a)
---[ end trace 89278304932c0e87 ]---
Kernel panic - not syncing: Fatal exception

Signed-off-by: Cheng Chao <cs.os.kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/staging/android/ion/ion_system_heap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/android/ion/ion_system_heap.c
+++ b/drivers/staging/android/ion/ion_system_heap.c
@@ -75,7 +75,7 @@ static struct page *alloc_buffer_page(st

page = ion_page_pool_alloc(pool);

- if (cached)
+ if (page && cached)
ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order,
DMA_BIDIRECTIONAL);
return page;