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Date:   Wed, 29 Nov 2017 15:59:27 +1100
From:   "Tobin C. Harding" <>
To:     Linus Torvalds <>
Cc:     LKML <>
Subject: [GIT PULL] hash addresses printed with %p

The following changes since commit 4fbd8d194f06c8a3fd2af1ce560ddb31f7ec8323:

  Linux 4.15-rc1 (2017-11-26 16:01:47 -0800)

are available in the git repository at:

  git:// tags/printk-hash-pointer-4.15-rc2

for you to fetch changes up to 6424f6bb432752c7eb90cbeeb1c31d6125bba39a:

  kasan: use %px to print addresses instead of %p (2017-11-29 12:13:16 +1100)

printk hashing patches for 4.15-rc2

Here is the patch set that implements hashing of printk specifier
%p. First we have two clean up patches then we do the hashing. Hashing
is done via the SipHash algorithm. The next patch adds printk specifier
%px for printing pointers when we _really_ want to see the address i.e
%px is functionally equivalent to %lx. Final patch in the set fixes
KASAN since we break it by hashing %p.

For the record here is the justification for the series.

Currently there exist approximately 14 000 places in the Kernel where
addresses are being printed using an unadorned %p. This potentially
leaks sensitive information about the Kernel layout in memory. Many of
these calls are stale, instead of fixing every call we can hash the
address by default before printing. We then add %px to provide a way to
print the actual address. Although this is achievable using %lx, using
%px will assist us if we ever want to change pointer printing
behaviour. %px is more uniquely grep'able (there are already > 50 000
uses of %lx).

The added advantage of hashing %p is that security is now opt-out, if
you _really_ want the address you have to work a little harder and use

This will of course break some users, forcing code printing needed
addresses to be updated.

Signed-off-by: Tobin C. Harding <>

Tobin C. Harding (5):
      docs: correct documentation for %pK
      vsprintf: refactor %pK code out of pointer()
      printk: hash addresses printed with %p
      vsprintf: add printk specifier %px
      kasan: use %px to print addresses instead of %p

 Documentation/printk-formats.txt |  31 ++++++-
 lib/test_printf.c                | 108 ++++++++++++++--------
 lib/vsprintf.c                   | 194 +++++++++++++++++++++++++++++----------
 mm/kasan/report.c                |   8 +-
 scripts/            |   2 +-
 5 files changed, 248 insertions(+), 95 deletions(-)

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