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To:     "Dalessandro, Dennis" <dennis.dalessandro@cornelisnetworks.com>,
        mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com,
        "jgg@ziepe.ca" <jgg@ziepe.ca>
Cc:     linux-rdma@vger.kernel.org,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        "baijiaju1990@gmail.com" <baijiaju1990@gmail.com>
From:   Tuo Li <islituo@gmail.com>
Subject: [BUG] RDMA/hw/qib/qib_iba6120: possible buffer underflow in
 rcvctrl_6120_mod()
Message-ID: <9c03a5f4-865b-000e-0206-9e01f876261a@gmail.com>
Date:   Thu, 12 Aug 2021 15:35:53 +0800
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Hello,

Our static analysis tool reports a possible buffer underflow in 
qib_iba6120.c in Linux 5.14.0-rc3:

The variable ctxt is checked in:
2110:    if (ctxt < 0)

This indicates that ctxt can be negative.
If so, possible buffer underflows will occur:
2120:    qib_write_kreg_ctxt(dd, kr_rcvhdrtailaddr, ctxt, 
dd->rcd[ctxt]->rcvhdrqtailaddr_phys);
2122:    qib_write_kreg_ctxt(dd, kr_rcvhdraddr, ctxt, 
dd->rcd[ctxt]->rcvhdrq_phys);

However, I am not sure whether ctxt < 0 and op & QIB_RCVCTRL_CTXT_ENB 
can be true at the same time.

Any feedback would be appreciated, thanks!

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>

Best wishes,
Tuo Li