On Fri, Feb 5, 2016 at 2:03 PM, Jason A. Donenfeld <ja...@zx2c4.com> wrote:
> The kptr_restrict flag, when set to 1, only prints the kernel
> address when the user has CAP_SYSLOG. When it is set to 2, the
> kernel address is always printed as zero. When set to 1, this
> needs to check whether or not we're in IRQ. However, when set to
> 2, this check is unneccessary, and produces confusing results
> in dmesg. Thus, only make sure we're not in IRQ when mode 1 is
> used, but not mode 2.
>
> Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com>
Thanks!
Acked-by: Kees Cook <keesc...@chromium.org>
-Kees
> ---
> lib/vsprintf.c | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 80d8ce5..ee1e24e 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1605,22 +1605,23 @@ char *pointer(const char *fmt, char *buf, char *end,
> void *ptr,
> return buf;
> }
> case 'K':
> - /*
> - * %pK cannot be used in IRQ context because its test
> - * for CAP_SYSLOG would be meaningless.
> - */
> - if (kptr_restrict && (in_irq() || in_serving_softirq() ||
> - in_nmi())) {
> - if (spec.field_width == -1)
> - spec.field_width = default_width;
> - return string(buf, end, "pK-error", spec);
> - }
> -
> switch (kptr_restrict) {
> case 0:
> /* Always print %pK values */
> break;
> case 1: {
> + const struct cred *cred;
> +
> + /*
> + * kptr_restrict==2 cannot be used in IRQ context
> because
> + * its test for CAP_SYSLOG would be meaningless.
> + */
> + if (in_irq() || in_serving_softirq() || in_nmi()) {
> + if (spec.field_width == -1)
> + spec.field_width = default_width;
> + return string(buf, end, "pK-error", spec);
> + }
> +
> /*
> * Only print the real pointer value if the current
> * process has CAP_SYSLOG and is running with the
> @@ -1630,8 +1631,7 @@ char *pointer(const char *fmt, char *buf, char *end,
> void *ptr,
> * leak pointer values if a binary opens a file using
> * %pK and then elevates privileges before reading it.
> */
> - const struct cred *cred = current_cred();
> -
> + cred = current_cred();
> if (!has_capability_noaudit(current, CAP_SYSLOG) ||
> !uid_eq(cred->euid, cred->uid) ||
> !gid_eq(cred->egid, cred->gid))
> --
> 2.7.0
>
--
Kees Cook
Chrome OS & Brillo Security
