diff options
author | Petr Mladek | 2021-02-22 13:43:26 +0100 |
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committer | Petr Mladek | 2021-02-22 13:43:26 +0100 |
commit | 2a8c3a6410f042e89e36df20b465845852aa3d9f (patch) | |
tree | 19e545ea1afa98744817d63426e7217e03322eea | |
parent | 8a8109f303e25a27f92c1d8edd67d7cbbc60a4eb (diff) | |
parent | 5ead723a20e0447bc7db33dc3070b420e5f80aa6 (diff) |
Merge branch 'for-5.12-no_hash_pointers' into for-linus
-rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 15 | ||||
-rw-r--r-- | lib/test_bitmap.c | 3 | ||||
-rw-r--r-- | lib/test_printf.c | 12 | ||||
-rw-r--r-- | lib/vsprintf.c | 36 | ||||
-rw-r--r-- | tools/testing/selftests/kselftest_module.h | 18 |
5 files changed, 72 insertions, 12 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c722ec19cd00..c549bc789108 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3281,6 +3281,21 @@ in certain environments such as networked servers or real-time systems. + no_hash_pointers + Force pointers printed to the console or buffers to be + unhashed. By default, when a pointer is printed via %p + format string, that pointer is "hashed", i.e. obscured + by hashing the pointer value. This is a security feature + that hides actual kernel addresses from unprivileged + users, but it also makes debugging the kernel more + difficult since unequal pointers can no longer be + compared. However, if this command-line option is + specified, then all normal pointers will have their true + value printed. Pointers printed via %pK may still be + hashed. This option should only be specified when + debugging the kernel. Please do not use on production + kernels. + nohibernate [HIBERNATION] Disable hibernation and resume. nohz= [KNL] Boottime enable/disable dynamic ticks diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c index 4425a1dd4ef1..0ea0e8258f14 100644 --- a/lib/test_bitmap.c +++ b/lib/test_bitmap.c @@ -16,8 +16,7 @@ #include "../tools/testing/selftests/kselftest_module.h" -static unsigned total_tests __initdata; -static unsigned failed_tests __initdata; +KSTM_MODULE_GLOBALS(); static char pbl_buffer[PAGE_SIZE] __initdata; diff --git a/lib/test_printf.c b/lib/test_printf.c index 7ac87f18a10f..a6755798e9e6 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -30,11 +30,13 @@ #define PAD_SIZE 16 #define FILL_CHAR '$' -static unsigned total_tests __initdata; -static unsigned failed_tests __initdata; +KSTM_MODULE_GLOBALS(); + static char *test_buffer __initdata; static char *alloced_buffer __initdata; +extern bool no_hash_pointers; + static int __printf(4, 0) __init do_test(int bufsize, const char *expect, int elen, const char *fmt, va_list ap) @@ -301,6 +303,12 @@ plain(void) { int err; + if (no_hash_pointers) { + pr_warn("skipping plain 'p' tests"); + skipped_tests += 2; + return; + } + err = plain_hash(); if (err) { pr_warn("plain 'p' does not appear to be hashed\n"); diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 3b53c73580c5..41ddc353ebb8 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2090,6 +2090,32 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode, return widen_string(buf, buf - buf_start, end, spec); } +/* Disable pointer hashing if requested */ +bool no_hash_pointers __ro_after_init; +EXPORT_SYMBOL_GPL(no_hash_pointers); + +static int __init no_hash_pointers_enable(char *str) +{ + no_hash_pointers = true; + + pr_warn("**********************************************************\n"); + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n"); + pr_warn("** **\n"); + pr_warn("** This system shows unhashed kernel memory addresses **\n"); + pr_warn("** via the console, logs, and other interfaces. This **\n"); + pr_warn("** might reduce the security of your system. **\n"); + pr_warn("** **\n"); + pr_warn("** If you see this message and you are not debugging **\n"); + pr_warn("** the kernel, report this immediately to your system **\n"); + pr_warn("** administrator! **\n"); + pr_warn("** **\n"); + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n"); + pr_warn("**********************************************************\n"); + + return 0; +} +early_param("no_hash_pointers", no_hash_pointers_enable); + /* * Show a '%p' thing. A kernel extension is that the '%p' is followed * by an extra set of alphanumeric characters that are extended format @@ -2297,8 +2323,14 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, } } - /* default is to _not_ leak addresses, hash before printing */ - return ptr_to_id(buf, end, ptr, spec); + /* + * default is to _not_ leak addresses, so hash before printing, + * unless no_hash_pointers is specified on the command line. + */ + if (unlikely(no_hash_pointers)) + return pointer_string(buf, end, ptr, spec); + else + return ptr_to_id(buf, end, ptr, spec); } /* diff --git a/tools/testing/selftests/kselftest_module.h b/tools/testing/selftests/kselftest_module.h index e8eafaf0941a..e2ea41de3f35 100644 --- a/tools/testing/selftests/kselftest_module.h +++ b/tools/testing/selftests/kselftest_module.h @@ -11,7 +11,8 @@ #define KSTM_MODULE_GLOBALS() \ static unsigned int total_tests __initdata; \ -static unsigned int failed_tests __initdata +static unsigned int failed_tests __initdata; \ +static unsigned int skipped_tests __initdata #define KSTM_CHECK_ZERO(x) do { \ total_tests++; \ @@ -21,11 +22,16 @@ static unsigned int failed_tests __initdata } \ } while (0) -static inline int kstm_report(unsigned int total_tests, unsigned int failed_tests) +static inline int kstm_report(unsigned int total_tests, unsigned int failed_tests, + unsigned int skipped_tests) { - if (failed_tests == 0) - pr_info("all %u tests passed\n", total_tests); - else + if (failed_tests == 0) { + if (skipped_tests) { + pr_info("skipped %u tests\n", skipped_tests); + pr_info("remaining %u tests passed\n", total_tests); + } else + pr_info("all %u tests passed\n", total_tests); + } else pr_warn("failed %u out of %u tests\n", failed_tests, total_tests); return failed_tests ? -EINVAL : 0; @@ -36,7 +42,7 @@ static int __init __module##_init(void) \ { \ pr_info("loaded.\n"); \ selftest(); \ - return kstm_report(total_tests, failed_tests); \ + return kstm_report(total_tests, failed_tests, skipped_tests); \ } \ static void __exit __module##_exit(void) \ { \ |