kern/128304: vn_pollrecord() derefs NULL if v_addpollinfo() fails
Doug White
dwhite at FreeBSD.org
Wed Oct 22 22:50:01 UTC 2008
>Number: 128304
>Category: kern
>Synopsis: vn_pollrecord() derefs NULL if v_addpollinfo() fails
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Oct 22 22:50:00 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator: Doug White
>Release: FreeBSD 7.0-RELEASE
>Organization:
Personal
>Environment:
FreeBSD mail1.sjc1.bitgravity.com 7.0-RELEASE-p4 FreeBSD 7.0-RELEASE-p4 #1: Mon Sep 29 18:30:06 PDT 2008 dwhite at mail1.sjc1.bitgravity.com:/usr/obj/usr/src/sys/BITGRAVITY amd64
>Description:
The first few lines of vn_pollrecord() are:
if (vp->v_pollinfo == NULL)
v_addpollinfo(vp);
mtx_lock(&vp->v_pollinfo->vpi_lock);
v_addpollinfo() leaves vp->v_pollinfo NULL if the malloc attempt fails. vfs_kqfilter() checks for failure, but this function does not. If allocation were to fail then the mtx_lock() call would result in a null pointer dereference panic.
>How-To-Repeat:
Problem was found by code inspection.
>Fix:
vn_pollrecord() should ensure v_addpollinfo() succeeds in allocating the pollinfo lists. However vn_pollrecord() uses its return value to convey the original event mask so there does not appear to be a method to return an error value (ENOMEM, etc.) in the current implementation.
>Release-Note:
>Audit-Trail:
>Unformatted:
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