Re: [PATCH] scsi: sg: Fix mismatch in sg_get_rq_mark

From: Andrey Konovalov
Date: Tue May 16 2017 - 10:55:43 EST


On Tue, May 16, 2017 at 4:52 PM, <firogm@xxxxxxxxx> wrote:
> From: Firo Yang <firogm@xxxxxxxxx>
>
> This bug was reported by Andrey Konovalov with syzkaller:
>
> Call Trace:
> sg_finish_rem_req+0x2a6/0x320 drivers/scsi/sg.c:1839
> sg_new_read+0x3c/0x430 drivers/scsi/sg.c:567
> sg_read+0x866/0x1830 drivers/scsi/sg.c:455
> __vfs_read+0x5c3/0x750 fs/read_write.c:450
> vfs_read+0x11e/0x350 fs/read_write.c:473
> SYSC_read fs/read_write.c:589
> SyS_read+0xfb/0x230 fs/read_write.c:582
> entry_SYSCALL_64_fastpath+0x1f/0xbe arch/x86/entry/entry_64.S:204
>
> If there is nothing matched in the loop of list_for_each_entry,
> at last the iteration variable 'resp' will point to
> list_entry(&sfp->rq_list, typeof(resp), entry); it's not a valid
> Sg_request. Finnally, 'resp' will be wrongly returned to the caller
> function.
>
> To fix it, add another return variable to record the correct
> match and return it to the caller function.

I think this was already fixed by https://lkml.org/lkml/2017/5/10/83

Thanks!

>
> Signed-off-by: Firo Yang <firogm@xxxxxxxxx>
> ---
> drivers/scsi/sg.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 0a38ba0..74a9188 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -2065,7 +2065,7 @@ sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp)
> static Sg_request *
> sg_get_rq_mark(Sg_fd * sfp, int pack_id)
> {
> - Sg_request *resp;
> + Sg_request *resp, *ret_resp = NULL;
> unsigned long iflags;
>
> write_lock_irqsave(&sfp->rq_list_lock, iflags);
> @@ -2074,11 +2074,12 @@ sg_get_rq_mark(Sg_fd * sfp, int pack_id)
> if ((1 == resp->done) && (!resp->sg_io_owned) &&
> ((-1 == pack_id) || (resp->header.pack_id == pack_id))) {
> resp->done = 2; /* guard against other readers */
> + ret_resp = resp;
> break;
> }
> }
> write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
> - return resp;
> + return ret_resp;
> }
>
> /* always adds to end of list */
> --
> 2.9.4
>
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