Re: [PATCH] Fix the kernel panic of audit_filter_task when key field is set

[zhangxiliang <zhangxiliang@cn.fujitsu.com>]

[PATCH] Fix the kernel panic of audit_filter_task when AUDIT_PERM or AUDIT_FILETYPE field is set

When calling audit_filter_task(), it calls audit_filter_rules() with audit_context is NULL.
If the AUDIT_PERM or AUDIT_FILETYPE field is set, audit_match_perm() or audit_match_filetype() will use ctx->xx.
But the ctx is NULL in this condition, so kernel will panic.

Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
---
 kernel/auditsc.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 012c94e..29b6964 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -243,6 +243,8 @@ static inline int open_arg(int flags, int mask)
 
 static int audit_match_perm(struct audit_context *ctx, int mask)
 {
+	if(!ctx)
+		return 0;
 	unsigned n = ctx->major;
 	switch (audit_classify_syscall(ctx->arch, n)) {
 	case 0:	/* native */
@@ -284,6 +286,8 @@ static int audit_match_filetype(struct audit_context *ctx, int which)
 {
 	unsigned index = which & ~S_IFMT;
 	mode_t mode = which & S_IFMT;
+	if(!ctx)
+		return 0;
 	if (index >= ctx->name_count)
 		return 0;
 	if (ctx->names[index].ino == -1)


zhangxiliang said the following on 2008-08-01 19:15:
> When calling audit_filter_task(), it calls audit_filter_rules() with audit_context is NULL.
> If the key field is set, the result in audit_filter_rules() will be set to 1 and 
> ctx->filterkey will be set to key.
> But the ctx is NULL in this condition, so kernel will panic.
> 
> Signed-off-by: Zhang Xiliang <zhangxiliang@cn.fujitsu.com>
> ---
>  kernel/auditsc.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 4699950..012c94e 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -610,7 +610,7 @@ static int audit_filter_rules(struct task_struct *tsk,
>  		if (!result)
>  			return 0;
>  	}
> -	if (rule->filterkey)
> +	if (rule->filterkey && ctx)
>  		ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
>  	switch (rule->action) {
>  	case AUDIT_NEVER:    *state = AUDIT_DISABLED;	    break;
> 
> --
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> 
> 
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