Patch "mmc: sdhci: fix low memory corruption" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

mmc: sdhci: fix low memory corruption

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mmc-sdhci-fix-low-memory-corruption.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jiri Slaby <[email protected]>
Date: Fri, 12 Jun 2015 11:45:02 +0200
Subject: mmc: sdhci: fix low memory corruption

From: Jiri Slaby <[email protected]>

commit 62a7f368ffbc13d9aedfdd7aeae711b177db69ac upstream.

When dma mapping (dma_map_sg) fails in sdhci_pre_dma_transfer, -EINVAL is returned. There are 3 callers of sdhci_pre_dma_transfer:
* sdhci_pre_req and sdhci_adma_table_pre: handle negative return
* sdhci_prepare_data: handles 0 (error) and "else" (good) only

sdhci_prepare_data is therefore broken. When it receives -EINVAL from sdhci_pre_dma_transfer, it assumes 1 sg mapping was mapped. Later, this non-existent mapping with address 0 is kmap'ped and written to:
Corrupted low memory at ffff880000001000 (1000 phys) = 22b7d67df2f6d1cf Corrupted low memory at ffff880000001008 (1008 phys) = 63848a5216b7dd95 Corrupted low memory at ffff880000001010 (1010 phys) = 330eb7ddef39e427 Corrupted low memory at ffff880000001018 (1018 phys) = 8017ac7295039bda Corrupted low memory at ffff880000001020 (1020 phys) = 8ce039eac119074f
...

So teach sdhci_prepare_data to understand negative return values from sdhci_pre_dma_transfer and disable DMA in that case, as well as for zero.

It was introduced in 348487cb28e66b032bae1b38424d81bf5b444408 (mmc:
sdhci: use pipeline mmc requests to improve performance). The commit seems to be suspicious also by assigning host->sg_count both in sdhci_pre_dma_transfer and sdhci_adma_table_pre.

---
 drivers/mmc/host/sdhci.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -846,7 +846,7 @@ static void sdhci_prepare_data(struct sd
 			int sg_cnt;
 
 			sg_cnt = sdhci_pre_dma_transfer(host, data, NULL);
-			if (sg_cnt == 0) {
+			if (sg_cnt <= 0) {
 				/*
 				 * This only happens when someone fed
 				 * us an invalid request.

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/mmc-sdhci-fix-low-memory-corruption.patch