net: convert %p usage to %pK

The %pK format specifier is designed to hide exposed kernel pointers,
specifically via /proc interfaces.  Exposing these pointers provides an
easy target for kernel write vulnerabilities, since they reveal the
locations of writable structures containing easily triggerable function
pointers.  The behavior of %pK depends on the kptr_restrict sysctl.

If kptr_restrict is set to 0, no deviation from the standard %p behavior
occurs.  If kptr_restrict is set to 1, the default, if the current user
(intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG
(currently in the LSM tree), kernel pointers using %pK are printed as 0's.
 If kptr_restrict is set to 2, kernel pointers using %pK are printed as
0's regardless of privileges.  Replacing with 0's was chosen over the
default "(null)", which cannot be parsed by userland %p, which expects
"(nil)".

The supporting code for kptr_restrict and %pK are currently in the -mm
tree.  This patch converts users of %p in net/ to %pK.  Cases of printing
pointers to the syslog are not covered, since this would eliminate useful
information for postmortem debugging and the reading of the syslog is
already optionally protected by the dmesg_restrict sysctl.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: James Morris <jmorris@namei.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Thomas Graf <tgraf@infradead.org>
Cc: Eugene Teo <eugeneteo@kernel.org>
Cc: Kees Cook <kees.cook@canonical.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David S. Miller <davem@davemloft.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 5 insertions, 5 deletions

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index ae64984f81a..cc7313b8f7e 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1240,7 +1240,7 @@ static void raw6_sock_seq_show(struct seq_file *seq, struct sock *sp, int i)
         srcp  = inet_sk(sp)->inet_num;
         seq_printf(seq,
                    "%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
-                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p %d\n",
+                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %pK %d\n",
                    i,
                    src->s6_addr32[0], src->s6_addr32[1],
                    src->s6_addr32[2], src->s6_addr32[3], srcp,
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 868366470b4..d1fd28711ba 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -2036,7 +2036,7 @@ static void get_openreq6(struct seq_file *seq,
 
         seq_printf(seq,
                    "%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
-                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p\n",
+                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %pK\n",
                    i,
                    src->s6_addr32[0], src->s6_addr32[1],
                    src->s6_addr32[2], src->s6_addr32[3],
@@ -2087,7 +2087,7 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
 
         seq_printf(seq,
                    "%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
-                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p %lu %lu %u %u %d\n",
+                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %pK %lu %lu %u %u %d\n",
                    i,
                    src->s6_addr32[0], src->s6_addr32[1],
                    src->s6_addr32[2], src->s6_addr32[3], srcp,
@@ -2129,7 +2129,7 @@ static void get_timewait6_sock(struct seq_file *seq,
 
         seq_printf(seq,
                    "%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
-                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p\n",
+                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %pK\n",
                    i,
                    src->s6_addr32[0], src->s6_addr32[1],
                    src->s6_addr32[2], src->s6_addr32[3], srcp,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index fc0c42a88e5..41f8c9c08db 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1391,7 +1391,7 @@ static void udp6_sock_seq_show(struct seq_file *seq, struct sock *sp, int bucket
         srcp  = ntohs(inet->inet_sport);
         seq_printf(seq,
                    "%5d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
-                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p %d\n",
+                   "%02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %pK %d\n",
                    bucket,
                    src->s6_addr32[0], src->s6_addr32[1],
                    src->s6_addr32[2], src->s6_addr32[3], srcp,