2021-12-14 03:35:37

by Xiaoke Wang

Subject: [PATCH] integrity: check the return value of audit_log_start()

From: Xiaoke Wang <[email protected]>

audit_log_start() returns audit_buffer pointer on success or NULL on
error, so it is better to check the return value of it to prevent
potential memory access error.

Signed-off-by: Xiaoke Wang <[email protected]>
---
security/integrity/integrity_audit.c | 38 +++++++++++++++-------------
1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
index 2922005..62785d5 100644
--- a/security/integrity/integrity_audit.c
+++ b/security/integrity/integrity_audit.c
@@ -45,23 +45,25 @@ void integrity_audit_message(int audit_msgno, struct inode *inode,
return;

ab = audit_log_start(audit_context(), GFP_KERNEL, audit_msgno);
- audit_log_format(ab, "pid=%d uid=%u auid=%u ses=%u",
- task_pid_nr(current),
- from_kuid(&init_user_ns, current_uid()),
- from_kuid(&init_user_ns, audit_get_loginuid(current)),
- audit_get_sessionid(current));
- audit_log_task_context(ab);
- audit_log_format(ab, " op=%s cause=%s comm=", op, cause);
- audit_log_untrustedstring(ab, get_task_comm(name, current));
- if (fname) {
- audit_log_format(ab, " name=");
- audit_log_untrustedstring(ab, fname);
+ if (ab) {
+ audit_log_format(ab, "pid=%d uid=%u auid=%u ses=%u",
+ task_pid_nr(current),
+ from_kuid(&init_user_ns, current_uid()),
+ from_kuid(&init_user_ns, audit_get_loginuid(current)),
+ audit_get_sessionid(current));
+ audit_log_task_context(ab);
+ audit_log_format(ab, " op=%s cause=%s comm=", op, cause);
+ audit_log_untrustedstring(ab, get_task_comm(name, current));
+ if (fname) {
+ audit_log_format(ab, " name=");
+ audit_log_untrustedstring(ab, fname);
+ }
+ if (inode) {
+ audit_log_format(ab, " dev=");
+ audit_log_untrustedstring(ab, inode->i_sb->s_id);
+ audit_log_format(ab, " ino=%lu", inode->i_ino);
+ }
+ audit_log_format(ab, " res=%d errno=%d", !result, errno);
+ audit_log_end(ab);
}
- if (inode) {
- audit_log_format(ab, " dev=");
- audit_log_untrustedstring(ab, inode->i_sb->s_id);
- audit_log_format(ab, " ino=%lu", inode->i_ino);
- }
- audit_log_format(ab, " res=%d errno=%d", !result, errno);
- audit_log_end(ab);
}
--

2022-01-12 17:23:23

by Paul Moore

Subject: Re: [PATCH] integrity: check the return value of audit_log_start()

On Tue, Dec 14, 2021 at 12:39 AM <[email protected]> wrote:
>
> From: Xiaoke Wang <[email protected]>
>
> audit_log_start() returns audit_buffer pointer on success or NULL on
> error, so it is better to check the return value of it to prevent
> potential memory access error.
>
> Signed-off-by: Xiaoke Wang <[email protected]>
> ---
> security/integrity/integrity_audit.c | 38 +++++++++++++++-------------
> 1 file changed, 20 insertions(+), 18 deletions(-)
>
> diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
> index 2922005..62785d5 100644
> --- a/security/integrity/integrity_audit.c
> +++ b/security/integrity/integrity_audit.c
> @@ -45,23 +45,25 @@ void integrity_audit_message(int audit_msgno, struct inode *inode,
> return;
>
> ab = audit_log_start(audit_context(), GFP_KERNEL, audit_msgno);

As this is IMA code, it's largely up to Mimi about what she would
prefer, but I think a much simpler patch would be to just return early
if ab == NULL, for example:

ab = audit_log_start( .... , audit_msgno);
if (!ab)
return;

> - audit_log_format(ab, "pid=%d uid=%u auid=%u ses=%u",
> - task_pid_nr(current),
> - from_kuid(&init_user_ns, current_uid()),
> - from_kuid(&init_user_ns, audit_get_loginuid(current)),
> - audit_get_sessionid(current));
> - audit_log_task_context(ab);
> - audit_log_format(ab, " op=%s cause=%s comm=", op, cause);
> - audit_log_untrustedstring(ab, get_task_comm(name, current));
> - if (fname) {
> - audit_log_format(ab, " name=");
> - audit_log_untrustedstring(ab, fname);
> + if (ab) {
> + audit_log_format(ab, "pid=%d uid=%u auid=%u ses=%u",
> + task_pid_nr(current),
> + from_kuid(&init_user_ns, current_uid()),
> + from_kuid(&init_user_ns, audit_get_loginuid(current)),
> + audit_get_sessionid(current));
> + audit_log_task_context(ab);
> + audit_log_format(ab, " op=%s cause=%s comm=", op, cause);
> + audit_log_untrustedstring(ab, get_task_comm(name, current));
> + if (fname) {
> + audit_log_format(ab, " name=");
> + audit_log_untrustedstring(ab, fname);
> + }
> + if (inode) {
> + audit_log_format(ab, " dev=");
> + audit_log_untrustedstring(ab, inode->i_sb->s_id);
> + audit_log_format(ab, " ino=%lu", inode->i_ino);
> + }
> + audit_log_format(ab, " res=%d errno=%d", !result, errno);
> + audit_log_end(ab);
> }
> - if (inode) {
> - audit_log_format(ab, " dev=");
> - audit_log_untrustedstring(ab, inode->i_sb->s_id);
> - audit_log_format(ab, " ino=%lu", inode->i_ino);
> - }
> - audit_log_format(ab, " res=%d errno=%d", !result, errno);
> - audit_log_end(ab);
> }
> --



--
paul moore
http://www.paul-moore.com

2022-01-18 03:04:25

by Mimi Zohar

Subject: Re: [PATCH] integrity: check the return value of audit_log_start()

On Wed, 2022-01-12 at 12:23 -0500, Paul Moore wrote:
> On Tue, Dec 14, 2021 at 12:39 AM <[email protected]> wrote:
> >
> > From: Xiaoke Wang <[email protected]>
> >
> > audit_log_start() returns audit_buffer pointer on success or NULL on
> > error, so it is better to check the return value of it to prevent
> > potential memory access error.
> >
> > Signed-off-by: Xiaoke Wang <[email protected]>
> > ---
> > security/integrity/integrity_audit.c | 38 +++++++++++++++-------------
> > 1 file changed, 20 insertions(+), 18 deletions(-)
> >
> > diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
> > index 2922005..62785d5 100644
> > --- a/security/integrity/integrity_audit.c
> > +++ b/security/integrity/integrity_audit.c
> > @@ -45,23 +45,25 @@ void integrity_audit_message(int audit_msgno, struct inode *inode,
> > return;
> >
> > ab = audit_log_start(audit_context(), GFP_KERNEL, audit_msgno);
>
> As this is IMA code, it's largely up to Mimi about what she would
> prefer, but I think a much simpler patch would be to just return early
> if ab == NULL, for example:
>
> ab = audit_log_start( .... , audit_msgno);
> if (!ab)
> return;

Thanks, Paul. Neither the linux-integrity mailing list nor I were
Cc'ed on this. Looks like the IMA & EVM records in MAINTAINERS should
be updated to include the security/integrity directory.

thanks,

Mimi