diff options
| -rw-r--r-- | Documentation/printk-formats.txt | 18 | ||||
| -rw-r--r-- | lib/vsprintf.c | 18 | ||||
| -rwxr-xr-x | scripts/checkpatch.pl | 2 |
3 files changed, 36 insertions, 2 deletions
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt index b4e668ac4fe3..aa0a776c817a 100644 --- a/Documentation/printk-formats.txt +++ b/Documentation/printk-formats.txt @@ -49,7 +49,8 @@ Pointer Types Pointers printed without a specifier extension (i.e unadorned %p) are hashed to give a unique identifier without leaking kernel addresses to user -space. On 64 bit machines the first 32 bits are zeroed. +space. On 64 bit machines the first 32 bits are zeroed. If you _really_ +want the address see %px below. :: @@ -106,6 +107,21 @@ For printing kernel pointers which should be hidden from unprivileged users. The behaviour of ``%pK`` depends on the ``kptr_restrict sysctl`` - see Documentation/sysctl/kernel.txt for more details. +Unmodified Addresses +==================== + +:: + + %px 01234567 or 0123456789abcdef + +For printing pointers when you _really_ want to print the address. Please +consider whether or not you are leaking sensitive information about the +Kernel layout in memory before printing pointers with %px. %px is +functionally equivalent to %lx. %px is preferred to %lx because it is more +uniquely grep'able. If, in the future, we need to modify the way the Kernel +handles printing pointers it will be nice to be able to find the call +sites. + Struct Resources ================ diff --git a/lib/vsprintf.c b/lib/vsprintf.c index d69452a0f2fa..d960aead0336 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1646,6 +1646,20 @@ char *device_node_string(char *buf, char *end, struct device_node *dn, return widen_string(buf, buf - buf_start, end, spec); } +static noinline_for_stack +char *pointer_string(char *buf, char *end, const void *ptr, + struct printf_spec spec) +{ + spec.base = 16; + spec.flags |= SMALL; + if (spec.field_width == -1) { + spec.field_width = 2 * sizeof(ptr); + spec.flags |= ZEROPAD; + } + + return number(buf, end, (unsigned long int)ptr, spec); +} + static bool have_filled_random_ptr_key __read_mostly; static siphash_key_t ptr_key __read_mostly; @@ -1818,6 +1832,8 @@ static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec) * c major compatible string * C full compatible string * + * - 'x' For printing the address. Equivalent to "%lx". + * * ** Please update also Documentation/printk-formats.txt when making changes ** * * Note: The difference between 'S' and 'F' is that on ia64 and ppc64 @@ -1940,6 +1956,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, case 'F': return device_node_string(buf, end, ptr, spec, fmt + 1); } + case 'x': + return pointer_string(buf, end, ptr, spec); } /* default is to _not_ leak addresses, hash before printing */ diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 95cda3ecc66b..040aa79e1d9d 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -5753,7 +5753,7 @@ sub process { for (my $count = $linenr; $count <= $lc; $count++) { my $fmt = get_quoted_string($lines[$count - 1], raw_line($count, 0)); $fmt =~ s/%%//g; - if ($fmt =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGNO]).)/) { + if ($fmt =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGNOx]).)/) { $bad_extension = $1; last; } |