On Mon, Aug 22, 2016 at 1:55 PM, <tom.t...@gmail.com> wrote:
> From: Tom Yan <tom.t...@gmail.com>
>
> In commit 5c79097a28c2 ("libata-scsi: reject WRITE SAME (16) with
> n_block that exceeds limit"), it is made sure that
> ata_set_lba_range_entries() will never be called with a request
> size (n_block) that is larger than the number of blocks that a
> 512-byte block TRIM payload can describe (65535 * 64 = 4194240),
> in addition to acknowlegding the SCSI/block layer with the same
> limit by advertising it as the Maximum Write Same Length.
>
> Therefore, it is unnecessary to hard code the same limit in
> ata_set_lba_range_entries() itself, which would only cost extra
> maintenance effort. Such effort can be noticed in, for example,
> commit 2983860c7668 ("libata-scsi: avoid repeated calculation of
> number of TRIM ranges").
>
> Signed-off-by: Tom Yan <tom.t...@gmail.com>
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index be9c76c..9b74ecb 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3322,7 +3322,7 @@ static unsigned int ata_scsi_write_same_xlat(struct
> ata_queued_cmd *qc)
> buf = page_address(sg_page(scsi_sglist(scmd)));
>
> if (n_block <= 65535 * ATA_MAX_TRIM_RNUM) {
> - size = ata_set_lba_range_entries(buf, ATA_MAX_TRIM_RNUM,
> block, n_block);
> + size = ata_set_lba_range_entries(buf, block, n_block);
> } else {
> fp = 2;
> goto invalid_fld;
> diff --git a/include/linux/ata.h b/include/linux/ata.h
> index adbc812..5e2e9ad 100644
> --- a/include/linux/ata.h
> +++ b/include/linux/ata.h
> @@ -1077,19 +1077,19 @@ static inline void ata_id_to_hd_driveid(u16 *id)
> * TO NV CACHE PINNED SET.
> */
> static inline unsigned ata_set_lba_range_entries(void *_buffer,
> - unsigned num, u64 sector, unsigned long count)
> + u64 sector, unsigned long count)
> {
> __le64 *buffer = _buffer;
> unsigned i = 0, used_bytes;
>
> - while (i < num) {
> - u64 entry = sector |
> - ((u64)(count > 0xffff ? 0xffff : count) << 48);
> + while (count > 0) {
> + u64 range, entry;
> +
> + range = count > 0xffff ? 0xffff : count;
> + entry = sector | (range << 48);
> buffer[i++] = __cpu_to_le64(entry);
> - if (count <= 0xffff)
> - break;
> - count -= 0xffff;
> - sector += 0xffff;
> + count -= range;
> + sector += range;
> }
I think the problem here is that I can now inject a buffer overflow
via SG_IO.
> used_bytes = ALIGN(i * 8, 512);
> --
> 2.9.3
>
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