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In kern_linkat() and kern_renameat(), do not call namei(9) while

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holding a write reference on the filesystem.  Try to get write
reference in unblocked way after all vnodes are resolved; if failed,
drop all locks and retry after waiting for suspension end.

The VFS_UNMOUNT() methods for UFS and tmpfs try to establish
suspension on unmount, while covered vnode is locked by VFS, which
prevents namei() from stepping over the mount point.  The thread doing
namei() sleeps on the covered vnode lock, owning the write ref.

Reported by:	bdrewery
Tested by:	bdrewery (previous version), pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-09-25 20:42:25 +00:00
parent 83e78a7f6e
commit 2c6fbcbed6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=272130
1 changed files with 56 additions and 29 deletions
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85
sys/kern/vfs_syscalls.c
View file

@ -1551,10 +1551,10 @@ kern_linkat(struct thread *td, int fd1, int fd2, char *path1, char *path2,
cap_rights_t rights;
int error;
again:
bwillwrite();
NDINIT_AT(&nd, LOOKUP, follow | AUDITVNODE1, segflg, path1, fd1, td);
again:
if ((error = namei(&nd)) != 0)
return (error);
NDFREE(&nd, NDF_ONLY_PNBUF);
@ -1563,50 +1563,65 @@ kern_linkat(struct thread *td, int fd1, int fd2, char *path1, char *path2,
vrele(vp);
return (EPERM); /* POSIX */
}
if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0) {
vrele(vp);
return (error);
}
NDINIT_ATRIGHTS(&nd, CREATE, LOCKPARENT | SAVENAME | AUDITVNODE2,
segflg, path2, fd2, cap_rights_init(&rights, CAP_LINKAT), td);
if ((error = namei(&nd)) == 0) {
if (nd.ni_vp != NULL) {
NDFREE(&nd, NDF_ONLY_PNBUF);
if (nd.ni_dvp == nd.ni_vp)
vrele(nd.ni_dvp);
else
vput(nd.ni_dvp);
vrele(nd.ni_vp);
error = EEXIST;
} else if ((error = vn_lock(vp, LK_EXCLUSIVE)) == 0) {
vrele(vp);
return (EEXIST);
} else if (nd.ni_dvp->v_mount != vp->v_mount) {
/*
* Check for cross-device links. No need to
* recheck vp->v_type, since it cannot change
* for non-doomed vnode.
* Cross-device link. No need to recheck
* vp->v_type, since it cannot change, except
* to VBAD.
*/
if (nd.ni_dvp->v_mount != vp->v_mount)
error = EXDEV;
else
error = can_hardlink(vp, td->td_ucred);
if (error == 0)
NDFREE(&nd, NDF_ONLY_PNBUF);
vput(nd.ni_dvp);
vrele(vp);
return (EXDEV);
} else if ((error = vn_lock(vp, LK_EXCLUSIVE)) == 0) {
error = can_hardlink(vp, td->td_ucred);
#ifdef MAC
if (error == 0)
error = mac_vnode_check_link(td->td_ucred,
nd.ni_dvp, vp, &nd.ni_cnd);
if (error == 0)
#endif
error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
if (error != 0) {
vput(vp);
vput(nd.ni_dvp);
NDFREE(&nd, NDF_ONLY_PNBUF);
return (error);
}
error = vn_start_write(vp, &mp, V_NOWAIT);
if (error != 0) {
vput(vp);
vput(nd.ni_dvp);
NDFREE(&nd, NDF_ONLY_PNBUF);
error = vn_start_write(NULL, &mp,
V_XSLEEP | PCATCH);
if (error != 0)
return (error);
goto again;
}
error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
VOP_UNLOCK(vp, 0);
vput(nd.ni_dvp);
vn_finished_write(mp);
NDFREE(&nd, NDF_ONLY_PNBUF);
} else {
vput(nd.ni_dvp);
NDFREE(&nd, NDF_ONLY_PNBUF);
vrele(vp);
vn_finished_write(mp);
goto again;
}
NDFREE(&nd, NDF_ONLY_PNBUF);
}
vrele(vp);
vn_finished_write(mp);
return (error);
}
@ -3519,6 +3534,7 @@ kern_renameat(struct thread *td, int oldfd, char *old, int newfd, char *new,
cap_rights_t rights;
int error;
again:
bwillwrite();
#ifdef MAC
NDINIT_ATRIGHTS(&fromnd, DELETE, LOCKPARENT | LOCKLEAF | SAVESTART |
@ -3539,14 +3555,6 @@ kern_renameat(struct thread *td, int oldfd, char *old, int newfd, char *new,
VOP_UNLOCK(fromnd.ni_vp, 0);
#endif
fvp = fromnd.ni_vp;
if (error == 0)
error = vn_start_write(fvp, &mp, V_WAIT | PCATCH);
if (error != 0) {
NDFREE(&fromnd, NDF_ONLY_PNBUF);
vrele(fromnd.ni_dvp);
vrele(fvp);
goto out1;
}
NDINIT_ATRIGHTS(&tond, RENAME, LOCKPARENT | LOCKLEAF | NOCACHE |
SAVESTART | AUDITVNODE2, pathseg, new, newfd,
cap_rights_init(&rights, CAP_LINKAT), td);
@ -3559,11 +3567,30 @@ kern_renameat(struct thread *td, int oldfd, char *old, int newfd, char *new,
NDFREE(&fromnd, NDF_ONLY_PNBUF);
vrele(fromnd.ni_dvp);
vrele(fvp);
vn_finished_write(mp);
goto out1;
}
tdvp = tond.ni_dvp;
tvp = tond.ni_vp;
error = vn_start_write(fvp, &mp, V_NOWAIT);
if (error != 0) {
NDFREE(&fromnd, NDF_ONLY_PNBUF);
NDFREE(&tond, NDF_ONLY_PNBUF);
if (tvp != NULL)
vput(tvp);
if (tdvp == tvp)
vrele(tdvp);
else
vput(tdvp);
vrele(fromnd.ni_dvp);
vrele(fvp);
vrele(tond.ni_startdir);
if (fromnd.ni_startdir != NULL)
vrele(fromnd.ni_startdir);
error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH);
if (error != 0)
return (error);
goto again;
}
if (tvp != NULL) {
if (fvp->v_type == VDIR && tvp->v_type != VDIR) {
error = ENOTDIR;