lkml.org 
[lkml]   [2021]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] lsm_audit,selinux: add exception handling for possible NULL audit buffers
On Mon, Jul 12, 2021 at 7:48 PM Austin Kim <austindh.kim@gmail.com> wrote:
> From: Austin Kim <austin.kim@lge.com>
>
> It is possible for audit_log_start() to return NULL on error.
> So add exception handling for possible NULL audit buffers where
> return value can be handled from callers.

Hi.

The patch looks fine to me, but I think the description doesn't tell
the full story and I'm worried that people might misunderstand why
this patch is worthwhile. I would suggest you revise the commit
description to explain that in these cases it is safe to return early
when audit_log_start() returns NULL because the only non-cleanup
processing left in these functions is to generate an audit record.
Returning early in these cases is a performance optimization and not a
correctness issue; the audit_log_*() functions can support being
passed a NULL audit_buffer argument.

> Signed-off-by: Austin Kim <austin.kim@lge.com>
> ---
> security/selinux/hooks.c | 4 ++++
> security/selinux/ss/services.c | 2 ++
> 2 files changed, 6 insertions(+)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index b0032c42333e..9e84e6635f2f 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3325,6 +3325,8 @@ static int selinux_inode_setxattr(struct user_namespace *mnt_userns,
> }
> ab = audit_log_start(audit_context(),
> GFP_ATOMIC, AUDIT_SELINUX_ERR);
> + if (!ab)
> + return rc;
> audit_log_format(ab, "op=setxattr invalid_context=");
> audit_log_n_untrustedstring(ab, value, audit_size);
> audit_log_end(ab);
> @@ -6552,6 +6554,8 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
> ab = audit_log_start(audit_context(),
> GFP_ATOMIC,
> AUDIT_SELINUX_ERR);
> + if (!ab)
> + return error;
> audit_log_format(ab, "op=fscreate invalid_context=");
> audit_log_n_untrustedstring(ab, value, audit_size);
> audit_log_end(ab);
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index d84c77f370dc..e5f1b2757a83 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -1673,6 +1673,8 @@ static int compute_sid_handle_invalid_context(
> if (context_struct_to_string(policydb, newcontext, &n, &nlen))
> goto out;
> ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_SELINUX_ERR);
> + if (!ab)
> + goto out;
> audit_log_format(ab,
> "op=security_compute_sid invalid_context=");
> /* no need to record the NUL with untrusted strings */
> --
> 2.20.1

--
paul moore
www.paul-moore.com

\
 
 \ /
  Last update: 2021-07-13 04:50    [W:0.042 / U:0.580 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site