vnodeops(9): Take exclusive lock in read/seek for f_offset update.
Otherwise concurrent readers/seekers might clobber it.
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4526d8b331
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@ -1,4 +1,4 @@
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/* $NetBSD: vfs_vnops.c,v 1.234 2022/07/18 04:30:30 thorpej Exp $ */
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/* $NetBSD: vfs_vnops.c,v 1.235 2022/08/06 21:21:10 riastradh Exp $ */
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/*-
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* Copyright (c) 2009 The NetBSD Foundation, Inc.
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@ -66,7 +66,7 @@
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.234 2022/07/18 04:30:30 thorpej Exp $");
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__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.235 2022/08/06 21:21:10 riastradh Exp $");
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#include "veriexec.h"
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@ -647,7 +647,10 @@ vn_read(file_t *fp, off_t *offset, struct uio *uio, kauth_cred_t cred,
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ioflag |= IO_ALTSEMANTICS;
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if (fflag & FDIRECT)
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ioflag |= IO_DIRECT;
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vn_lock(vp, LK_SHARED | LK_RETRY);
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if (offset == &fp->f_offset && (flags & FOF_UPDATE_OFFSET) != 0)
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vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
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else
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vn_lock(vp, LK_SHARED | LK_RETRY);
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uio->uio_offset = *offset;
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count = uio->uio_resid;
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error = VOP_READ(vp, uio, ioflag, cred);
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@ -1135,7 +1138,10 @@ vn_seek(struct file *fp, off_t delta, int whence, off_t *newoffp,
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if (vp->v_type == VFIFO)
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return ESPIPE;
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vn_lock(vp, LK_SHARED | LK_RETRY);
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if (flags & FOF_UPDATE_OFFSET)
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vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
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else
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vn_lock(vp, LK_SHARED | LK_RETRY);
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/* Compute the old and new offsets. */
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oldoff = fp->f_offset;
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