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Fix a race between getvnode() dereferencing half-constructed file

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and dupfdopen().

Reported and tested by:	pho
MFC after:	3 days
This commit is contained in:
Konstantin Belousov 2011-11-24 20:34:06 +00:00
parent 24d1b19ec4
commit 561984be06
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=227952
1 changed files with 14 additions and 1 deletions
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15
sys/kern/vfs_syscalls.c
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@ -4344,7 +4344,20 @@ getvnode(struct filedesc *fdp, int fd, cap_rights_t rights,
fp = fp_fromcap;
}
#endif /* CAPABILITIES */
if (fp->f_vnode == NULL) {
/*
* The file could be not of the vnode type, or it may be not
* yet fully initialized, in which case the f_vnode pointer
* may be set, but f_ops is still badfileops. E.g.,
* devfs_open() transiently create such situation to
* facilitate csw d_fdopen().
*
* Dupfdopen() handling in kern_openat() installs the
* half-baked file into the process descriptor table, allowing
* other thread to dereference it. Guard against the race by
* checking f_ops.
*/
if (fp->f_vnode == NULL || fp->f_ops == &badfileops) {
fdrop(fp, curthread);
return (EINVAL);
}