linux-kernel - [PATCH resend 5/9] MIPS: sync after cacheflush

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <17d8d27a2356640a4359f1a7dcbb3b42@localhost>
Date:	Sat, 16 Oct 2010 14:22:34 -0700
From:	Kevin Cernekee <cernekee@...il.com>
To:	Ralf Baechle <ralf@...ux-mips.org>
Cc:	<linux-mips@...ux-mips.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH resend 5/9] MIPS: sync after cacheflush

On processors with deep write buffers, it is likely that many cycles
will pass between a CACHE instruction and the time the data actually
gets written out to DRAM.  Add a SYNC instruction to ensure that the
buffers get emptied before the flush functions return.

Actual problem seen in the wild:

1) dma_alloc_coherent() allocates cached memory

2) memset() is called to clear the new pages

3) dma_cache_wback_inv() is called to flush the zero data out to memory

4) dma_alloc_coherent() returns an uncached (kseg1) pointer to the
freshly allocated pages

5) Caller writes data through the kseg1 pointer

6) Buffered writeback data finally gets flushed out to DRAM

7) Part of caller's data is inexplicably zeroed out

This patch adds SYNC between steps 3 and 4, which fixed the problem.

Signed-off-by: Kevin Cernekee <cernekee@...il.com>
---
 arch/mips/mm/c-r4k.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 6721ee2..05c3de3 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -605,6 +605,7 @@ static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size)
 			r4k_blast_scache();
 		else
 			blast_scache_range(addr, addr + size);
+		__sync();
 		return;
 	}
 
@@ -621,6 +622,7 @@ static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size)
 	}
 
 	bc_wback_inv(addr, size);
+	__sync();
 }
 
 static void r4k_dma_cache_inv(unsigned long addr, unsigned long size)
@@ -648,6 +650,7 @@ static void r4k_dma_cache_inv(unsigned long addr, unsigned long size)
 				 (addr + size - 1) & almask);
 			blast_inv_scache_range(addr, addr + size);
 		}
+		__sync();
 		return;
 	}
 
@@ -664,6 +667,7 @@ static void r4k_dma_cache_inv(unsigned long addr, unsigned long size)
 	}
 
 	bc_inv(addr, size);
+	__sync();
 }
 #endif /* CONFIG_DMA_NONCOHERENT */
 
-- 
1.7.0.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/