linux-kernel - [PATCH 4.20 62/80] IB/hfi1: Remove overly conservative VM

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Message-Id: <20190204103628.770342559@linuxfoundation.org>
Date:   Mon,  4 Feb 2019 11:37:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        "Michael J. Ruhl" <michael.j.ruhl@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>
Subject: [PATCH 4.20 62/80] IB/hfi1: Remove overly conservative VM_EXEC flag check

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael J. Ruhl <michael.j.ruhl@...el.com>

commit 7709b0dc265f28695487712c45f02bbd1f98415d upstream.

Applications that use the stack for execution purposes cause userspace PSM
jobs to fail during mmap().

Both Fortran (non-standard format parsing) and C (callback functions
located in the stack) applications can be written such that stack
execution is required. The linker notes this via the gnu_stack ELF flag.

This causes READ_IMPLIES_EXEC to be set which forces all PROT_READ mmaps
to have PROT_EXEC for the process.

Checking for VM_EXEC bit and failing the request with EPERM is overly
conservative and will break any PSM application using executable stacks.

Cc: <stable@...r.kernel.org> #v4.14+
Fixes: 12220267645c ("IB/hfi: Protect against writable mmap")
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@...el.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@...el.com>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@...el.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@...el.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/infiniband/hw/hfi1/file_ops.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/hw/hfi1/file_ops.c
+++ b/drivers/infiniband/hw/hfi1/file_ops.c
@@ -488,7 +488,7 @@ static int hfi1_file_mmap(struct file *f
 		vmf = 1;
 		break;
 	case STATUS:
-		if (flags & (unsigned long)(VM_WRITE | VM_EXEC)) {
+		if (flags & VM_WRITE) {
 			ret = -EPERM;
 			goto done;
 		}