| Message ID | 20200702232638.2946421-4-keescook@chromium.org |
|---|---|
| State | Not Applicable |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | Refactor kallsyms_show_value() users for correct cred | expand |
+++ Kees Cook [02/07/20 16:26 -0700]: >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. > >Cc: stable@vger.kernel.org >Reported-by: Dominik Czarnota <dominik.czarnota@trailofbits.com> >Fixes: be71eda5383f ("module: Fix display of wrong module .text address") >Signed-off-by: Kees Cook <keescook@chromium.org> Tested-by: Jessica Yu <jeyu@kernel.org> Acked-by: Jessica Yu <jeyu@kernel.org>
diff --git a/kernel/module.c b/kernel/module.c index 9e2954519259..e6c7571092cb 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1530,8 +1530,8 @@ static ssize_t module_sect_read(struct file *file, struct kobject *kobj, 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) @@ -4380,7 +4380,7 @@ static int modules_open(struct inode *inode, struct file *file) 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;
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. Cc: stable@vger.kernel.org Reported-by: Dominik Czarnota <dominik.czarnota@trailofbits.com> Fixes: be71eda5383f ("module: Fix display of wrong module .text address") Signed-off-by: Kees Cook <keescook@chromium.org> --- kernel/module.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)