From bfa4133795e5a0badd402dd3f58b13b3cec64a4b Mon Sep 17 00:00:00 2001 From: Cyrille Pitchen Date: Wed, 6 Sep 2017 23:45:02 +0200 Subject: [PATCH] mtd: spi-nor: fix DMA unsafe buffer issue in spi_nor_read_sfdp() spi_nor_read_sfdp() calls nor->read() to read the SFDP data. When the m25p80 driver is used (pretty common case), nor->read() is then implemented by the m25p80_read() function, which is likely to initialize a 'struct spi_transfer' from its buf argument before appending this structure inside the 'struct spi_message' argument of spi_sync(). Besides the SPI sub-system states that both .tx_buf and .rx_buf members of 'struct spi_transfer' must point into dma-safe memory. However, two of the three calls of spi_nor_read_sfdp() were given pointers to stack allocated memory as buf argument, hence not in a dma-safe area. Hopefully, the third and last call of spi_nor_read_sfdp() was already given a kmalloc'ed buffer argument, hence dma-safe. So this patch fixes this issue by introducing a spi_nor_read_sfdp_dma_unsafe() function which simply wraps the existing spi_nor_read_sfdp() function and uses some kmalloc'ed memory as a bounce buffer. Fixes: f384b352cbf0 ("mtd: spi-nor: parse Serial Flash Discoverable Parameters (SFDP) tables") Reported-by: Geert Uytterhoeven Signed-off-by: Cyrille Pitchen Signed-off-by: Boris Brezillon --- drivers/mtd/spi-nor/spi-nor.c | 36 ++++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index 4425b0283725..19c000722cbc 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -1784,7 +1784,7 @@ spi_nor_set_pp_settings(struct spi_nor_pp_command *pp, * @nor: pointer to a 'struct spi_nor' * @addr: offset in the SFDP area to start reading data from * @len: number of bytes to read - * @buf: buffer where the SFDP data are copied into + * @buf: buffer where the SFDP data are copied into (dma-safe memory) * * Whatever the actual numbers of bytes for address and dummy cycles are * for (Fast) Read commands, the Read SFDP (5Ah) instruction is always @@ -1829,6 +1829,36 @@ read_err: return ret; } +/** + * spi_nor_read_sfdp_dma_unsafe() - read Serial Flash Discoverable Parameters. + * @nor: pointer to a 'struct spi_nor' + * @addr: offset in the SFDP area to start reading data from + * @len: number of bytes to read + * @buf: buffer where the SFDP data are copied into + * + * Wrap spi_nor_read_sfdp() using a kmalloc'ed bounce buffer as @buf is now not + * guaranteed to be dma-safe. + * + * Return: -ENOMEM if kmalloc() fails, the return code of spi_nor_read_sfdp() + * otherwise. + */ +static int spi_nor_read_sfdp_dma_unsafe(struct spi_nor *nor, u32 addr, + size_t len, void *buf) +{ + void *dma_safe_buf; + int ret; + + dma_safe_buf = kmalloc(len, GFP_KERNEL); + if (!dma_safe_buf) + return -ENOMEM; + + ret = spi_nor_read_sfdp(nor, addr, len, dma_safe_buf); + memcpy(buf, dma_safe_buf, len); + kfree(dma_safe_buf); + + return ret; +} + struct sfdp_parameter_header { u8 id_lsb; u8 minor; @@ -2101,7 +2131,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor, bfpt_header->length * sizeof(u32)); addr = SFDP_PARAM_HEADER_PTP(bfpt_header); memset(&bfpt, 0, sizeof(bfpt)); - err = spi_nor_read_sfdp(nor, addr, len, &bfpt); + err = spi_nor_read_sfdp_dma_unsafe(nor, addr, len, &bfpt); if (err < 0) return err; @@ -2252,7 +2282,7 @@ static int spi_nor_parse_sfdp(struct spi_nor *nor, int i, err; /* Get the SFDP header. */ - err = spi_nor_read_sfdp(nor, 0, sizeof(header), &header); + err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sizeof(header), &header); if (err < 0) return err; -- 2.20.1