From ace16862006efd4ce025bf54997cdb20584d0fe4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Draszik?= Date: Thu, 22 Feb 2018 10:21:46 +0000 Subject: ramips: mt7620: eMMC: stop invalid memory access if only one device is defined MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit pdev->id is -1 when only one device exists, and is used: * as an index into drv_mode[] to determine whether to use PIO or DMA mode (via host->id) * as an index into msdc_6575_host[], to store the mmc_priv() data. Obviously, -1 is not a valid index in either case, causing us to read invalid memory, and memory corruption, respectively. The invalid memory read is causing non-deterministic behaviour, in particular in the v4.4 kernel it still picked DMA mode, but in the v4.9 it now always picks PIO mode. Also, PIO mode doesn't work, causing the following: / # echo 3 > /proc/sys/vm/drop_caches [ 3845.249237] sh (128): drop_caches: 3 / # /root/usr/lib/libc.so [ 3846.096070] do_page_fault(): sending SIGSEGV to libc.so for invalid read access from 7f9cb5a0 [ 3846.104758] epc = 779b0ea4 in libc.so[7792f000+c3000] [ 3846.109907] ra = 779a8004 in libc.so[7792f000+c3000] Segmentation fault / # /root/usr/lib/libc.so musl libc (mipsel-sf) Version 1.1.16-git-40-g54807d47 Dynamic Program Loader Usage: /root/usr/lib/libc.so [options] [--] pathname [args] (i.e. initial page-in of any binary causes a segfault, subsequent access works.) While this change doesn't fix PIO mode, it at least makes us deterministically use DMA (which works), and it also stops us from corrupting memory. Signed-off-by: André Draszik --- .../0046-mmc-MIPS-ralink-add-sdhci-for-mt7620a-SoC.patch | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'target/linux/ramips/patches-4.9/0046-mmc-MIPS-ralink-add-sdhci-for-mt7620a-SoC.patch') diff --git a/target/linux/ramips/patches-4.9/0046-mmc-MIPS-ralink-add-sdhci-for-mt7620a-SoC.patch b/target/linux/ramips/patches-4.9/0046-mmc-MIPS-ralink-add-sdhci-for-mt7620a-SoC.patch index 7dd25b1d40..da3c0772b5 100644 --- a/target/linux/ramips/patches-4.9/0046-mmc-MIPS-ralink-add-sdhci-for-mt7620a-SoC.patch +++ b/target/linux/ramips/patches-4.9/0046-mmc-MIPS-ralink-add-sdhci-for-mt7620a-SoC.patch @@ -1761,7 +1761,7 @@ Signed-off-by: John Crispin + --- /dev/null +++ b/drivers/mmc/host/mtk-mmc/sd.c -@@ -0,0 +1,3066 @@ +@@ -0,0 +1,3068 @@ +/* Copyright Statement: + * + * This software/firmware and related documentation ("MediaTek Software") are @@ -4572,7 +4572,9 @@ Signed-off-by: John Crispin + host = mmc_priv(mmc); + host->hw = hw; + host->mmc = mmc; -+ host->id = pdev->id; ++ BUG_ON(pdev->id < -1); ++ BUG_ON(pdev->id >= ARRAY_SIZE(drv_mode)); ++ host->id = (pdev->id == -1) ? 0 : pdev->id; + host->error = 0; + host->irq = irq; + host->base = (unsigned long) base; -- cgit v1.2.3