| From b25a7c5af9051850d4f3d93ca500056ab6ec724b Mon Sep 17 00:00:00 2001 |
| From: Kees Cook <keescook@chromium.org> |
| Date: Thu, 2 Jul 2020 14:43:59 -0700 |
| Subject: module: Do not expose section addresses to non-CAP_SYSLOG |
| |
| From: Kees Cook <keescook@chromium.org> |
| |
| commit b25a7c5af9051850d4f3d93ca500056ab6ec724b upstream. |
| |
| The printing of section addresses in /sys/module/*/sections/* was not |
| using the correct credentials to evaluate visibility. |
| |
| Before: |
| |
| # cat /sys/module/*/sections/.*text |
| 0xffffffffc0458000 |
| ... |
| # capsh --drop=CAP_SYSLOG -- -c "cat /sys/module/*/sections/.*text" |
| 0xffffffffc0458000 |
| ... |
| |
| After: |
| |
| # cat /sys/module/*/sections/*.text |
| 0xffffffffc0458000 |
| ... |
| # capsh --drop=CAP_SYSLOG -- -c "cat /sys/module/*/sections/.*text" |
| 0x0000000000000000 |
| ... |
| |
| Additionally replaces the existing (safe) /proc/modules check with |
| file->f_cred for consistency. |
| |
| Reported-by: Dominik Czarnota <dominik.czarnota@trailofbits.com> |
| Fixes: be71eda5383f ("module: Fix display of wrong module .text address") |
| Cc: stable@vger.kernel.org |
| Tested-by: Jessica Yu <jeyu@kernel.org> |
| Acked-by: Jessica Yu <jeyu@kernel.org> |
| Signed-off-by: Kees Cook <keescook@chromium.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| kernel/module.c | 6 +++--- |
| 1 file changed, 3 insertions(+), 3 deletions(-) |
| |
| --- a/kernel/module.c |
| +++ b/kernel/module.c |
| @@ -1527,8 +1527,8 @@ static ssize_t module_sect_read(struct f |
| if (pos != 0) |
| return -EINVAL; |
| |
| - return sprintf(buf, "0x%px\n", kptr_restrict < 2 ? |
| - (void *)sattr->address : NULL); |
| + return sprintf(buf, "0x%px\n", |
| + kallsyms_show_value(file->f_cred) ? (void *)sattr->address : NULL); |
| } |
| |
| static void free_sect_attrs(struct module_sect_attrs *sect_attrs) |
| @@ -4394,7 +4394,7 @@ static int modules_open(struct inode *in |
| |
| if (!err) { |
| struct seq_file *m = file->private_data; |
| - m->private = kallsyms_show_value(current_cred()) ? NULL : (void *)8ul; |
| + m->private = kallsyms_show_value(file->f_cred) ? NULL : (void *)8ul; |
| } |
| |
| return err; |