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    Subject[PATCH 5.13 704/800] mtd: spi-nor: otp: return -EROFS if region is read-only
    Date
    From: Michael Walle <michael@walle.cc>

    [ Upstream commit 388161ca45c911f566b71716bce5ff0119fb5522 ]

    SPI NOR flashes will just ignore program commands if the OTP region is
    locked. Thus, a user might not notice that the intended write didn't end
    up in the flash. Return -EROFS to the user in this case. From what I can
    tell, chips/cfi_cmdset_0001.c also return this error code.

    One could optimize spi_nor_mtd_otp_range_is_locked() to read the status
    register only once and not for every OTP region, but for that we would
    need some more invasive changes. Given that this is
    one-time-programmable memory and the normal access mode is reading, we
    just live with the small overhead.

    By moving the code around a bit, we can just check the length before
    calling spi_nor_mtd_otp_range_is_locked() and avoid an underflow there
    if a len is 0. This way we don't need to take the lock either. We also
    skip the "*retlen = 0" assignment, mtdcore already takes care of that
    for us.

    Fixes: 069089acf88b ("mtd: spi-nor: add OTP support")
    Signed-off-by: Michael Walle <michael@walle.cc>
    Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
    Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
    Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/mtd/spi-nor/otp.c | 41 ++++++++++++++++++++++++++++++++++++---
    1 file changed, 38 insertions(+), 3 deletions(-)

    diff --git a/drivers/mtd/spi-nor/otp.c b/drivers/mtd/spi-nor/otp.c
    index 5c51a2c9be61..d8e68120a4b1 100644
    --- a/drivers/mtd/spi-nor/otp.c
    +++ b/drivers/mtd/spi-nor/otp.c
    @@ -238,6 +238,29 @@ out:
    return ret;
    }

    +static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, loff_t ofs,
    + size_t len)
    +{
    + const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
    + unsigned int region;
    + int locked;
    +
    + /*
    + * If any of the affected OTP regions are locked the entire range is
    + * considered locked.
    + */
    + for (region = spi_nor_otp_offset_to_region(nor, ofs);
    + region <= spi_nor_otp_offset_to_region(nor, ofs + len - 1);
    + region++) {
    + locked = ops->is_locked(nor, region);
    + /* take the branch it is locked or in case of an error */
    + if (locked)
    + return locked;
    + }
    +
    + return 0;
    +}
    +
    static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
    size_t total_len, size_t *retlen,
    const u8 *buf, bool is_write)
    @@ -253,14 +276,26 @@ static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
    if (ofs < 0 || ofs >= spi_nor_otp_size(nor))
    return 0;

    + /* don't access beyond the end */
    + total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);
    +
    + if (!total_len)
    + return 0;
    +
    ret = spi_nor_lock_and_prep(nor);
    if (ret)
    return ret;

    - /* don't access beyond the end */
    - total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);
    + if (is_write) {
    + ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, total_len);
    + if (ret < 0) {
    + goto out;
    + } else if (ret) {
    + ret = -EROFS;
    + goto out;
    + }
    + }

    - *retlen = 0;
    while (total_len) {
    /*
    * The OTP regions are mapped into a contiguous area starting
    --
    2.30.2


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