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Date: Fri, 19 Sep 2014 11:41:15 -0400 From: Richard Guy Briggs <rgb@...hat.com> To: linux-security-module@...r.kernel.org, linux-audit@...hat.com, linux-kernel@...r.kernel.org Cc: Richard Guy Briggs <rgb@...hat.com>, pmoore@...hat.com, eparis@...hat.com, sgrubb@...hat.com, Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> Subject: [PATCH] lsm: get comm using lock to avoid race in string printing When task->comm is passed directly to audit_log_untrustedstring() without getting a copy or using the task_lock, there is a race that could happen that would output a NULL (\0) in the output string that would effectively truncate the rest of the report text after the comm= field in the audit, losing fields. Use get_task_comm() to get a copy while acquiring the task_lock to prevent this and to prevent the result from being a mixture of old and new values of comm. Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> Signed-off-by: Richard Guy Briggs <rgb@...hat.com> --- I've manually checked for locking issues and found none. I've also enabled all the kernel lock debugging options and it came up clean. security/lsm_audit.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/security/lsm_audit.c b/security/lsm_audit.c index 69fdf3b..4773b91 100644 --- a/security/lsm_audit.c +++ b/security/lsm_audit.c @@ -212,6 +212,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, struct common_audit_data *a) { struct task_struct *tsk = current; + char comm[sizeof(tsk->comm)]; /* * To keep stack sizes in check force programers to notice if they @@ -221,7 +222,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2); audit_log_format(ab, " pid=%d comm=", task_pid_nr(tsk)); - audit_log_untrustedstring(ab, tsk->comm); + audit_log_untrustedstring(ab, get_task_comm(comm, tsk)); switch (a->type) { case LSM_AUDIT_DATA_NONE: @@ -282,7 +283,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, pid_t pid = task_pid_nr(tsk); if (pid) { audit_log_format(ab, " pid=%d comm=", pid); - audit_log_untrustedstring(ab, tsk->comm); + audit_log_untrustedstring(ab, get_task_comm(comm, tsk)); } } break; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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