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Date: Mon, 12 Mar 2018 17:50:27 +0100
From: Salvatore Mesoraca <s.mesoraca16@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>, linux-scsi@...r.kernel.org,
"James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>,
"Tobin C. Harding" <tobin@...orbit.com>, Dario Ballabio <ballabio_dario@....com>,
Kees Cook <keescook@...omium.org>, Salvatore Mesoraca <s.mesoraca16@...il.com>, valdis.kletnieks@...edu
Subject: Re: [PATCH v2] scsi: eata: drop VLA in reorder()
2018-03-12 13:48 GMT+01:00 Salvatore Mesoraca <s.mesoraca16@...il.com>:
> Avoid 3 VLAs[1] by using a single dinamically allocated array
> and some helper variables: we don't need 3 arrays.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
> ---
> drivers/scsi/eata.c | 40 ++++++++++++++++++++++++++--------------
> 1 file changed, 26 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/scsi/eata.c b/drivers/scsi/eata.c
> index 6501c33..8ba44b7 100644
> --- a/drivers/scsi/eata.c
> +++ b/drivers/scsi/eata.c
> @@ -2091,12 +2091,14 @@ static void sort(unsigned long sk[], unsigned int da[], unsigned int n,
> static int reorder(struct hostdata *ha, unsigned long cursec,
> unsigned int ihdlr, unsigned int il[], unsigned int n_ready)
> {
> + int overlap;
> struct scsi_cmnd *SCpnt;
> struct mscp *cpp;
> unsigned int k, n;
> unsigned int rev = 0, s = 1, r = 1;
> - unsigned int input_only = 1, overlap = 0;
> - unsigned long sl[n_ready], pl[n_ready], ll[n_ready];
> + unsigned int input_only = 1;
> + unsigned long *sl;
> + unsigned long sl_zero, sl_cur, sl_prev, ll_cur, ll_prev;
> unsigned long maxsec = 0, minsec = ULONG_MAX, seek = 0, iseek = 0;
> unsigned long ioseek = 0;
>
> @@ -2115,6 +2117,12 @@ static int reorder(struct hostdata *ha, unsigned long cursec,
> if (n_ready <= 1)
> return 0;
>
> + overlap = -ENOMEM;
> + sl = kcalloc(n_ready, sizeof(*sl), GFP_ATOMIC);
I should have used kmalloc_array :/
Sending v3
> + if (!sl)
> + goto out;
> + overlap = 0;
> +
> for (n = 0; n < n_ready; n++) {
> k = il[n];
> cpp = &ha->cp[k];
> @@ -2164,31 +2172,33 @@ static int reorder(struct hostdata *ha, unsigned long cursec,
> if (!((rev && r) || (!rev && s)))
> sort(sl, il, n_ready, rev);
>
> + sl_zero = sl[0];
> +
> if (!input_only)
> for (n = 0; n < n_ready; n++) {
> k = il[n];
> cpp = &ha->cp[k];
> SCpnt = cpp->SCpnt;
> - ll[n] = blk_rq_sectors(SCpnt->request);
> - pl[n] = SCpnt->serial_number;
> + ll_cur = blk_rq_sectors(SCpnt->request);
> + sl_cur = sl[n];
> + sl[n] = SCpnt->serial_number;
>
> - if (!n)
> - continue;
> -
> - if ((sl[n] == sl[n - 1])
> - || (!rev && ((sl[n - 1] + ll[n - 1]) > sl[n]))
> - || (rev && ((sl[n] + ll[n]) > sl[n - 1])))
> + if (n && ((sl_cur == sl_prev)
> + || (!rev && ((sl_prev + ll_prev) > sl_cur))
> + || (rev && ((sl_cur + ll_cur) > sl_prev))))
> overlap = 1;
> + ll_prev = ll_cur;
> + sl_prev = sl_cur;
> }
>
> if (overlap)
> - sort(pl, il, n_ready, 0);
> + sort(sl, il, n_ready, 0);
>
> if (link_statistics) {
> - if (cursec > sl[0])
> - iseek = cursec - sl[0];
> + if (cursec > sl_zero)
> + iseek = cursec - sl_zero;
> else
> - iseek = sl[0] - cursec;
> + iseek = sl_zero - cursec;
> batchcount++;
> readycount += n_ready;
> seeknosort += seek / 1024;
> @@ -2225,6 +2235,8 @@ static int reorder(struct hostdata *ha, unsigned long cursec,
> YESNO(overlap), cpp->din);
> }
> #endif
> + kfree(sl);
> +out:
> return overlap;
> }
>
> --
> 1.9.1
>
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