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UPSTREAM: lib/vsprintf: no_hash_pointers prints all addresses as unhashed

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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

(cherry picked from commit 5ead723a20e0447bc7db33dc3070b420e5f80aa6)
Bug: 181049978
Change-Id: I06c5cfdc0b4c12f38c9109179f27bf2b54ac57e8
Signed-off-by: Chris Goldsworthy <cgoldswo@codeaurora.org>
This commit is contained in:
Timur Tabi
2021-02-14 10:13:48 -06:00
committed by Suren Baghdasaryan
parent 0e1b1c2d68
commit fc461a19b0
3 changed files with 57 additions and 2 deletions
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36
lib/vsprintf.c
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@@ -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);
}
/*