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authorPhilippe Mathieu-Daudé <philmd@redhat.com>2021-06-01 18:25:48 +0200
committerKevin Wolf <kwolf@redhat.com>2021-06-02 14:29:14 +0200
commitb317006a3f1f04191a7981cef83417cb2477213b (patch)
treef06e9cf601b25a7c63607750a70b2c0a2921bed6 /docs
parentbed9523471c13a44cdc15ed9ba0fb78cadf8c142 (diff)
docs/secure-coding-practices: Describe how to use 'null-co' block driver
Document that security reports must use 'null-co,read-zeroes=on' because otherwise the memory is left uninitialized (which is an on-purpose performance feature). Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> Message-Id: <20210601162548.2076631-1-philmd@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'docs')
-rw-r--r--docs/devel/secure-coding-practices.rst9
1 files changed, 9 insertions, 0 deletions
diff --git a/docs/devel/secure-coding-practices.rst b/docs/devel/secure-coding-practices.rst
index cbfc8af67e..0454cc527e 100644
--- a/docs/devel/secure-coding-practices.rst
+++ b/docs/devel/secure-coding-practices.rst
@@ -104,3 +104,12 @@ structures and only process the local copy. This prevents
time-of-check-to-time-of-use (TOCTOU) race conditions that could cause QEMU to
crash when a vCPU thread modifies guest RAM while device emulation is
processing it.
+
+Use of null-co block drivers
+----------------------------
+
+The ``null-co`` block driver is designed for performance: its read accesses are
+not initialized by default. In case this driver has to be used for security
+research, it must be used with the ``read-zeroes=on`` option which fills read
+buffers with zeroes. Security issues reported with the default
+(``read-zeroes=off``) will be discarded.