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The RC/UC code path can go through a software loopback. In this code path
the receive side QP is manipulated.
If two threads are working on the QP receive side (i.e. post_send, and
modify_qp to an error state), QP information can be corrupted.
(post_send via loopback)
set r_sge
loop
update r_sge
(modify_qp)
take r_lock
update r_sge <---- r_sge is now incorrect
(post_send)
update r_sge <---- crash, etc.
...
This can lead to one of the two following crashes:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: hfi1_copy_sge+0xf1/0x2e0 [hfi1]
PGD 8000001fe6a57067 PUD 1fd9e0c067 PMD 0
Call Trace:
ruc_loopback+0x49b/0xbc0 [hfi1]
hfi1_do_send+0x38e/0x3e0 [hfi1]
_hfi1_do_send+0x1e/0x20 [hfi1]
process_one_work+0x17f/0x440
worker_thread+0x126/0x3c0
kthread+0xd1/0xe0
ret_from_fork_nospec_begin+0x21/0x21
or:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
IP: rvt_clear_mr_refs+0x45/0x370 [rdmavt]
PGD 80000006ae5eb067 PUD ef15d0067 PMD 0
Call Trace:
rvt_error_qp+0xaa/0x240 [rdmavt]
rvt_modify_qp+0x47f/0xaa0 [rdmavt]
ib_security_modify_qp+0x8f/0x400 [ib_core]
ib_modify_qp_with_udata+0x44/0x70 [ib_core]
modify_qp.isra.23+0x1eb/0x2b0 [ib_uverbs]
ib_uverbs_modify_qp+0xaa/0xf0 [ib_uverbs]
ib_uverbs_write+0x272/0x430 [ib_uverbs]
vfs_write+0xc0/0x1f0
SyS_write+0x7f/0xf0
system_call_fastpath+0x1c/0x21
Fix by using the appropriate locking on the receiving QP.
Fixes: 1570346153 ("IB/{hfi1, qib, rdmavt}: Move ruc_loopback to rdmavt")
Cc: <stable@vger.kernel.org> #v4.9+
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.