On 22/11/17 03:23, Eric Yang wrote:
-----Original Message-----
From: Konrad Rzeszutek Wilk [mailto:[email protected]]
Sent: Tuesday, November 21, 2017 12:27 AM
To: Eric Yang <[email protected]>; [email protected]
Cc: [email protected]; Greg Kroah-Hartman
<[email protected]>; Andrew Morton <[email protected]>;
Andrey Ryabinin <[email protected]>; David Miller
<[email protected]>; Ingo Molnar <[email protected]>; Geert
Uytterhoeven <[email protected]>; Al Viro <[email protected]>;
Kees Cook <[email protected]>; Daniel Borkmann
<[email protected]>
Subject: Re: No check of the size passed to unmap_single in swiotlb
On Mon, Nov 20, 2017 at 08:17:14AM +0000, Eric Yang wrote:
Hi all,
Hi!
Hi Konrad,
During debug a device only support 32bits DMA(Qualcomm Atheros AP) in our
LS1043A 64bits ARM SOC, we found that the invoke of dma_unmap_single -->
swiotlb_tbl_unmap_single will unmap the passed "size" anyway even when the
"size" is incorrect.
If the size is larger than it should, the extra entries in io_tlb_orig_addr
array
will be refilled by INVALID_PHYS_ADDR, and it will cause the bounce buffer copy
not happen when the one who really used the mis-freed entries doing DMA data
transfers, and this will cause further unknow behaviors.
Here we just fix it temporarily by adding a judge of the "size" in the
swiotlb_tbl_unmap_single, if it is larger than it deserves, just unmap the right
size only. Like the code:
Did the DMA debug API (CONFIG_DMA_API_DEBUG) help in figuring this issue as
well?
I have just enabled this config and move off the kernel fix and test, there
seems the debug API
has no output for this size incorrect issue. For I only enable the config and
no other operations
and my kernel is 4.9, do I missed something?
I confirm that the debug API is working, for there are other drivers triggered
its warning output
like:
caam_jr 1710000.jr: DMA-API: device driver tries to free DMA memory it has not allocated
[device address=0x6800458400000000]
By default, dma-debug will only log the first error it sees - you can
adjust this with the "num_errors" or "all_errors" sysfs controls, and
use the driver filter to hide errors from other drivers if necessary.
Robin.
[yangyu@titan dash-lts]$ git diff ./lib/swiotlb.c diff --git
a/lib/swiotlb.c b/lib/swiotlb.c index ad1d2962d129..58c97ede9d78
100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -591,7 +591,10 @@ void swiotlb_tbl_unmap_single(struct device *hwdev,
phys_addr_t tlb_addr,
*/
for (i = index + nslots - 1; i >= index; i--) {
io_tlb_list[i] = ++count;
- io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+ if(io_tlb_orig_addr[i] != orig_addr)
+ printk("======size wrong, ally down ally
down!===\n");
+ else
+ io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
}
/*
* Step 2: merge the returned slots with the preceding
slots,
Although pass a right size of DMA buffer is the responsibility of the drivers,
but
Is it useful to add some size check code to prevent real damage happen?
Regards,
Eric
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