staging:rts_pstor:Fix possible panic by NULL pointer dereference

rtsx_transport.c (rtsx_transfer_sglist_adma_partial):
pointer struct scatterlist *sg, which is mapped in dma_map_sg,
is used as an iterator in later transfer operation. It is corrupted and
passed to dma_unmap_sg, thus causing fatal unmap of some erroneous address.
Fix it by duplicating *sg_ptr for iterating.

Signed-off-by: wwang <wei_wang@realsil.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/rts_pstor/rtsx_transport.c b/drivers/staging/rts_pstor/rtsx_transport.c
index 4e3d2c1..9b2e5c9 100644 (file)
--- a/drivers/staging/rts_pstor/rtsx_transport.c
+++ b/drivers/staging/rts_pstor/rtsx_transport.c
@@ -335,6 +335,7 @@ static int rtsx_transfer_sglist_adma_partial(struct rtsx_chip *chip, u8 card,
        int sg_cnt, i, resid;
        int err = 0;
        long timeleft;
+       struct scatterlist *sg_ptr;
        u32 val = TRIG_DMA;
 
        if ((sg == NULL) || (num_sg <= 0) || !offset || !index)
@@ -371,7 +372,7 @@ static int rtsx_transfer_sglist_adma_partial(struct rtsx_chip *chip, u8 card,
        sg_cnt = dma_map_sg(&(rtsx->pci->dev), sg, num_sg, dma_dir);
 
        resid = size;
-
+       sg_ptr = sg;
        chip->sgi = 0;
        /* Usually the next entry will be @sg@ + 1, but if this sg element
         * is part of a chained scatterlist, it could jump to the start of
@@ -379,14 +380,14 @@ static int rtsx_transfer_sglist_adma_partial(struct rtsx_chip *chip, u8 card,
         * the proper sg
         */
        for (i = 0; i < *index; i++)
-               sg = sg_next(sg);
+               sg_ptr = sg_next(sg_ptr);
        for (i = *index; i < sg_cnt; i++) {
                dma_addr_t addr;
                unsigned int len;
                u8 option;
 
-               addr = sg_dma_address(sg);
-               len = sg_dma_len(sg);
+               addr = sg_dma_address(sg_ptr);
+               len = sg_dma_len(sg_ptr);
 
                RTSX_DEBUGP("DMA addr: 0x%x, Len: 0x%x\n",
                             (unsigned int)addr, len);
@@ -415,7 +416,7 @@ static int rtsx_transfer_sglist_adma_partial(struct rtsx_chip *chip, u8 card,
                if (!resid)
                        break;
 
-               sg = sg_next(sg);
+               sg_ptr = sg_next(sg_ptr);
        }
 
        RTSX_DEBUGP("SG table count = %d\n", chip->sgi);