Date: Thu, 7 Jan 2016 12:08:15 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r293314 - in stable/10/sys: kern sys Message-ID: <201601071208.u07C8FUZ076869@repo.freebsd.org>
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Author: mjg Date: Thu Jan 7 12:08:15 2016 New Revision: 293314 URL: https://svnweb.freebsd.org/changeset/base/293314 Log: MFC r292440: proc: fix a race which could result in dereference of bad p_pgrp pointer on fork During fork p_starcopy - p_endcopy area of a process is populated with bcopy with only proc lock held. Another forking thread can find such a process and proceed to access p_pgrp included in said area. Fix the problem by moving the field outside. It is being properly assigned later. Modified: stable/10/sys/kern/kern_proc.c stable/10/sys/sys/proc.h Modified: stable/10/sys/kern/kern_proc.c ============================================================================== --- stable/10/sys/kern/kern_proc.c Thu Jan 7 11:54:20 2016 (r293313) +++ stable/10/sys/kern/kern_proc.c Thu Jan 7 12:08:15 2016 (r293314) @@ -234,6 +234,7 @@ proc_init(void *mem, int size, int flags TAILQ_INIT(&p->p_threads); /* all threads in proc */ EVENTHANDLER_INVOKE(process_init, p); p->p_stats = pstats_alloc(); + p->p_pgrp = NULL; SDT_PROBE3(proc, kernel, init, return, p, size, flags); return (0); } Modified: stable/10/sys/sys/proc.h ============================================================================== --- stable/10/sys/sys/proc.h Thu Jan 7 11:54:20 2016 (r293313) +++ stable/10/sys/sys/proc.h Thu Jan 7 12:08:15 2016 (r293314) @@ -558,7 +558,7 @@ struct proc { int p_osrel; /* (x) osreldate for the binary (from ELF note, if any) */ char p_comm[MAXCOMLEN + 1]; /* (b) Process name. */ - struct pgrp *p_pgrp; /* (c + e) Pointer to process group. */ + void *p_pad0; struct sysentvec *p_sysent; /* (b) Syscall dispatch info. */ struct pargs *p_args; /* (c) Process arguments. */ rlim_t p_cpulimit; /* (c) Current CPU limit in seconds. */ @@ -604,6 +604,7 @@ struct proc { pid_t p_reapsubtree; /* (e) Pid of the direct child of the reaper which spawned our subtree. */ + struct pgrp *p_pgrp; /* (c + e) Pointer to process group. */ }; #define p_session p_pgrp->pg_session
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