Messages in this thread | | | Date | Sun, 02 Sep 2018 16:01:44 -0700 (PDT) | Subject | Re: [PATCH] net: scm: Fix a possible sleep-in-atomic-context bug in scm_fp_copy() | From | David Miller <> |
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From: Jia-Ju Bai <baijiaju1990@gmail.com> Date: Sat, 1 Sep 2018 18:00:26 +0800
> The kernel module may sleep with holding a spinlock. > > The function call paths (from bottom to top) in Linux-4.16 are: > > [FUNC] kmalloc(GFP_KERNEL) > net/core/scm.c, 85: kmalloc in scm_fp_copy > net/core/scm.c, 161: scm_fp_copy in __scm_send > ./include/net/scm.h, 88: __scm_send in scm_send > net/unix/af_unix.c, 1600: scm_send in maybe_init_creds > net/unix/af_unix.c, 1983: maybe_init_creds in unix_stream_sendpage > net/unix/af_unix.c, 1973: spin_lock in unix_stream_sendpage
Please, do a full analysis of the code for these changes you are submitting.
Read maybe_init_creds(), it sets msg.msg_controllen to zero.
struct msghdr msg = { .msg_controllen = 0 };
When that is zero, __scm__send() is never called.
static __inline__ int scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm, bool forcecreds) { ... if (msg->msg_controllen <= 0) return 0; return __scm_send(sock, msg, scm);
If this bug existed, sleeping in atomic warnings would be triggering all the time and people would report that.
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