Commit 47016b34 authored Apr 23, 2018 by Thor Thayer Committed by Boris Brezillon Apr 23, 2018

mtd: spi-nor: cadence-quadspi: Fix page fault kernel panic



The current Cadence QSPI driver caused a kernel panic when loading
a Root Filesystem from QSPI. The problem was caused by reading more
bytes than needed because the QSPI operated on 4 bytes at a time.
<snip>
[    7.947754] spi_nor_read[1048]:from 0x037cad74, len 1 [bfe07fff]
[    7.956247] cqspi_read[910]:offset 0x58502516, buffer=bfe07fff
[    7.956247]
[    7.966046] Unable to handle kernel paging request at virtual
address bfe08002
[    7.973239] pgd = eebfc000
[    7.975931] [bfe08002] *pgd=2fffb811, *pte=00000000, *ppte=00000000
</snip>
Notice above how only 1 byte needed to be read but by reading 4 bytes
into the end of a mapped page, an unrecoverable page fault occurred.

This patch uses a temporary buffer to hold the 4 bytes read and then
copies only the bytes required into the buffer. A min() function is
used to limit the length to prevent buffer overflows.

Request testing of this patch on other platforms. This was tested
on the Intel Arria10 SoCFPGA DevKit.

Fixes: 0cf17256 ("mtd: spi-nor: cqspi: Fix build on arches missing readsl/writesl")
Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

parent 23566c37

drivers/mtd/spi-nor/cadence-quadspi.c

+17 −2

Original line number	Diff line number	Diff line
		@@ -501,7 +501,9 @@ static int cqspi_indirect_read_execute(struct spi_nor nor, u8 rxbuf,
		void __iomem *reg_base = cqspi->iobase;
		void __iomem *ahb_base = cqspi->ahb_base;
		unsigned int remaining = n_rx;
		unsigned int mod_bytes = n_rx % 4;
		unsigned int bytes_to_read = 0;
		u8 *rxbuf_end = rxbuf + n_rx;
		int ret = 0;

		writel(from_addr, reg_base + CQSPI_REG_INDIRECTRDSTARTADDR);
		@@ -530,11 +532,24 @@ static int cqspi_indirect_read_execute(struct spi_nor nor, u8 rxbuf,
		}

		while (bytes_to_read != 0) {
		unsigned int word_remain = round_down(remaining, 4);

		bytes_to_read *= cqspi->fifo_width;
		bytes_to_read = bytes_to_read > remaining ?
		remaining : bytes_to_read;
		bytes_to_read = round_down(bytes_to_read, 4);
		/* Read 4 byte word chunks then single bytes */
		if (bytes_to_read) {
		ioread32_rep(ahb_base, rxbuf,
		DIV_ROUND_UP(bytes_to_read, 4));
		(bytes_to_read / 4));
		} else if (!word_remain && mod_bytes) {
		unsigned int temp = ioread32(ahb_base);

		bytes_to_read = mod_bytes;
		memcpy(rxbuf, &temp, min((unsigned int)
		(rxbuf_end - rxbuf),
		bytes_to_read));
		}
		rxbuf += bytes_to_read;
		remaining -= bytes_to_read;
		bytes_to_read = cqspi_get_rd_sram_level(cqspi);