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| author | Timur Tabi <timur@kernel.org> | 2021-02-14 19:13:48 +0300 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2021-02-15 13:08:32 +0300 |
| commit | 5ead723a20e0447bc7db33dc3070b420e5f80aa6 (patch) | |
| tree | 48c75744ea69ab8a453743e41ab00d3c8a642839 /Documentation/admin-guide/kernel-parameters.txt | |
| parent | d9d4de2309cd1721421c6488f1bb5744d2c83a39 (diff) | |
| download | linux-5ead723a20e0447bc7db33dc3070b420e5f80aa6.tar.xz | |
lib/vsprintf: no_hash_pointers prints all addresses as unhashed
If the no_hash_pointers command line parameter is set, then
printk("%p") will print pointers as unhashed, which is useful for
debugging purposes. This change applies to any function that uses
vsprintf, such as print_hex_dump() and seq_buf_printf().
A large warning message is displayed if this option is enabled.
Unhashed pointers expose kernel addresses, which can be a security
risk.
Also update test_printf to skip the hashed pointer tests if the
command-line option is set.
Signed-off-by: Timur Tabi <timur@kernel.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210214161348.369023-4-timur@kernel.org
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 15 |
1 files changed, 15 insertions, 0 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 |