Messages in this thread Patch in this message | | | From | Petr Mladek <> | Subject | [PATCH v7 02/10] vsprintf: Consistent %pK handling for kptr_restrict == 0 | Date | Wed, 17 Apr 2019 13:53:42 +0200 |
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restricted_pointer() pretends that it prints the address when kptr_restrict is set to zero. But it is never called in this situation. Instead, pointer() falls back to ptr_to_id() and hashes the pointer.
This patch removes the potential confusion. klp_restrict is checked only in restricted_pointer().
It actually fixes a small race when the address might get printed unhashed:
CPU0 CPU1
pointer() if (!kptr_restrict) /* for example set to 2 */ restricted_pointer() /* echo 0 >/proc/sys/kernel/kptr_restrict */ proc_dointvec_minmax_sysadmin() klpr_restrict = 0; switch(kptr_restrict) case 0: break:
number()
Fixes: commit ef0010a30935de4e0211 ("vsprintf: don't use 'restricted_pointer()' when not restricting") Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Tobin Harding <me@tobin.cc> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> --- lib/vsprintf.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index eb7b4a06e1f0..2af48948a973 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -725,8 +725,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr, { switch (kptr_restrict) { case 0: - /* Always print %pK values */ - break; + /* Handle as %p, hash and do _not_ leak addresses. */ + return ptr_to_id(buf, end, ptr, spec); case 1: { const struct cred *cred; @@ -2041,8 +2041,6 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, return buf; } case 'K': - if (!kptr_restrict) - break; return restricted_pointer(buf, end, ptr, spec); case 'N': return netdev_bits(buf, end, ptr, spec, fmt); -- 2.16.4
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