[cip-dev] CVE-2020-12770: easy backport of sg code

["Pavel Machek" <pavel@ucw.cz>]

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Hi!

So let me investigate... Mainline fix is commit 83c6f2390040f188cc25b270b4befeb5628c1aee.

Backport for 4.19 looks really easy, and I can't see anything wrong
there:

commit c45e3bcdebb204ef1ba1d00f41fe7ed39c4dd8cd
Author: Pavel Machek <pavel@ucw.cz>
Date:   Thu May 14 23:47:42 2020 +0200

    Backport.
    
    commit 83c6f2390040f188cc25b270b4befeb5628c1aee
    ...
        scsi: sg: add sg_remove_request in sg_write
    
        If the __copy_from_user function failed we need to call
        sg_remove_request
            in sg_write.
    
     Link: https://lore.kernel.org/r/610618d9-e983-fd56-ed0f-639428343af7@huawei.com
     Acked-by: Douglas Gilbert <dgilbert@interlog.com>
     Signed-off-by: Wu Bo <wubo40@huawei.com>
     Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 8a254bb46a9b..4f00d3062bd6 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -694,8 +694,10 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
 	hp->flags = input_size;	/* structure abuse ... */
 	hp->pack_id = old_hdr.pack_id;
 	hp->usr_ptr = NULL;
-	if (__copy_from_user(cmnd, buf, cmd_size))
+	if (__copy_from_user(cmnd, buf, cmd_size)) {
+		sg_remove_request(sfp, srp);
 		return -EFAULT;
+	}
 	/*
 	 * SG_DXFER_TO_FROM_DEV is functionally equivalent to SG_DXFER_FROM_DEV,
 	 * but is is possible that the app intended SG_DXFER_TO_DEV, because there

And I don't see a problem with 4.4, either.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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