> -----邮件原件----- > 发件人: Paul Moore [mailto:[email protected]] > 发送时间: 2019年3月5日 22:18 > 收件人: Li,Rongqing <[email protected]> > 抄送: Eric Paris <[email protected]>; [email protected]; > [email protected] > 主题: Re: [PATCH] audit: fix a memleak caused by auditing load module > > On Tue, Mar 5, 2019 at 6:14 AM Li RongQing <[email protected]> wrote: > > we should always free context->module.name, since it will be allocated > > unconditionally and audit_log_start() can fail with other reasons, and > > audit_log_exit maybe not called > > > > unreferenced object 0xffff88af90837d20 (size 8): > > comm "modprobe", pid 1036, jiffies 4294704867 (age 3069.138s) > > hex dump (first 8 bytes): > > 69 78 67 62 65 00 ff ff ixgbe... > > backtrace: > > [<0000000008da28fe>] __audit_log_kern_module+0x33/0x80 > > [<00000000c1491e61>] load_module+0x64f/0x3850 > > [<000000007fc9ae3f>] __do_sys_init_module+0x218/0x250 > > [<0000000000d4a478>] do_syscall_64+0x117/0x400 > > [<000000004924ded8>] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > [<000000007dc331dd>] 0xffffffffffffffff > > > > Fixes: ca86cad7380e3 ("audit: log module name on init_module") > > Signed-off-by: Zhang Yu <[email protected]> > > Signed-off-by: Li RongQing <[email protected]> > > --- > > kernel/auditsc.c | 22 ++++++++++++++++++++-- > > 1 file changed, 20 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c index > > b2d1f043f..2bd80375f 100644 > > --- a/kernel/auditsc.c > > +++ b/kernel/auditsc.c > > @@ -1186,8 +1186,13 @@ static void show_special(struct audit_context > *context, int *call_panic) > > int i; > > > > ab = audit_log_start(context, GFP_KERNEL, context->type); > > - if (!ab) > > + if (!ab) { > > + if (context->type == AUDIT_KERN_MODULE) { > > + kfree(context->module.name); > > + context->module.name = NULL; > > + } > > return; > > + } > > Hello. > > Thanks for the patch, but I have to ask if you've considered freeing the > module > name in audit_free_context()? That seems like the correct way to solve this > issue. >
It does not work that move the freeing of module.name in audit_free_context Since we should free module.name based on context->types is AUDIT_KERN_MODULE, but __audit_syscall_exit is called first, and will set context->type to 0, When audit_free_context is called, context->type is 0, will cause to fail. I will change this patches as below: commit ee32ec2354b47a824e5e63d4f46567d577a02824 (HEAD -> master) Author: Li RongQing <[email protected]> Date: Tue Mar 5 15:42:09 2019 +0800 audit: fix a memleak caused by auditing load module module.name will be allocated unconditionally when auditing load module, and audit_log_start() can fail with other reasons, or audit_log_exit maybe not called, caused module.name is released so always free module.name in audit_free_context unreferenced object 0xffff88af90837d20 (size 8): comm "modprobe", pid 1036, jiffies 4294704867 (age 3069.138s) hex dump (first 8 bytes): 69 78 67 62 65 00 ff ff ixgbe... backtrace: [<0000000008da28fe>] __audit_log_kern_module+0x33/0x80 [<00000000c1491e61>] load_module+0x64f/0x3850 [<000000007fc9ae3f>] __do_sys_init_module+0x218/0x250 [<0000000000d4a478>] do_syscall_64+0x117/0x400 [<000000004924ded8>] entry_SYSCALL_64_after_hwframe+0x49/0xbe [<000000007dc331dd>] 0xffffffffffffffff Fixes: ca86cad7380e3 ("audit: log module name on init_module") Signed-off-by: Zhang Yu <[email protected]> Signed-off-by: Li RongQing <[email protected]> diff --git a/kernel/auditsc.c b/kernel/auditsc.c index b2d1f043f..07728b07a 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -964,6 +964,9 @@ int audit_alloc(struct task_struct *tsk) static inline void audit_free_context(struct audit_context *context) { + if (context->type == AUDIT_KERN_MODULE) + kfree(context->module.name); + audit_free_names(context); unroll_tree_refs(context, NULL, 0); free_tree_refs(context); @@ -1282,6 +1285,8 @@ static void show_special(struct audit_context *context, int *call_panic) if (context->module.name) { audit_log_untrustedstring(ab, context->module.name); kfree(context->module.name); + context->module.name = NULL; + context->type = 0; } else audit_log_format(ab, "(null)"); @@ -1583,6 +1588,11 @@ void __audit_syscall_exit(int success, long return_code) if (!list_empty(&context->killed_trees)) audit_kill_trees(&context->killed_trees); + if (context->type == AUDIT_KERN_MODULE) { + kfree(context->module.name); + context->module.name = NULL; + } + audit_free_names(context); unroll_tree_refs(context, NULL, 0); audit_free_aux(context); -RongQing > -Paul > > -- > paul moore > www.paul-moore.com
