mmc: core: Avoid negative index with array access

commit cf55a7acd1ed38afe43bba1c8a0935b51d1dc014 upstream.

Commit 4d0c8d0aef63 ("mmc: core: Use mrq.sbc in close-ended ffu") assigns
prev_idata = idatas[i - 1], but doesn't check that the iterator i is
greater than zero. Let's fix this by adding a check.

Fixes: 4d0c8d0aef63 ("mmc: core: Use mrq.sbc in close-ended ffu")
Link: https://lore.kernel.org/all/20231129092535.3278-1-avri.altman@wdc.com/
Cc: stable@vger.kernel.org
Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Tested-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Link: https://lore.kernel.org/r/20240313133744.2405325-2-mikko.rapeli@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index d2f78af5c5a719ac949e624de1e5500603fd6d1b..68f820cd73b27683bc52f6106a133e8d69206a52 100644 (file)
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -485,7 +485,7 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
        if (idata->flags & MMC_BLK_IOC_DROP)
                return 0;
 
-       if (idata->flags & MMC_BLK_IOC_SBC)
+       if (idata->flags & MMC_BLK_IOC_SBC && i > 0)
                prev_idata = idatas[i - 1];
 
        /*