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vnodeops(9): Take exclusive lock in read/seek for f_offset update. 

Otherwise concurrent readers/seekers might clobber it.
This commit is contained in:
riastradh 2022-08-06 21:21:10 +00:00
parent 4526d8b331
commit 2473fd3d55
1 changed files with 10 additions and 4 deletions
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14
sys/kern/vfs_vnops.c
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@ -1,4 +1,4 @@
/* $NetBSD: vfs_vnops.c,v 1.234 2022/07/18 04:30:30 thorpej Exp $ */
/* $NetBSD: vfs_vnops.c,v 1.235 2022/08/06 21:21:10 riastradh Exp $ */
/*-
* Copyright (c) 2009 The NetBSD Foundation, Inc.
@ -66,7 +66,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.234 2022/07/18 04:30:30 thorpej Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.235 2022/08/06 21:21:10 riastradh Exp $");
#include "veriexec.h"
@ -647,7 +647,10 @@ vn_read(file_t *fp, off_t *offset, struct uio *uio, kauth_cred_t cred,
ioflag |= IO_ALTSEMANTICS;
if (fflag & FDIRECT)
ioflag |= IO_DIRECT;
vn_lock(vp, LK_SHARED | LK_RETRY);
if (offset == &fp->f_offset && (flags & FOF_UPDATE_OFFSET) != 0)
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
else
vn_lock(vp, LK_SHARED | LK_RETRY);
uio->uio_offset = *offset;
count = uio->uio_resid;
error = VOP_READ(vp, uio, ioflag, cred);
@ -1135,7 +1138,10 @@ vn_seek(struct file *fp, off_t delta, int whence, off_t *newoffp,
if (vp->v_type == VFIFO)
return ESPIPE;
vn_lock(vp, LK_SHARED | LK_RETRY);
if (flags & FOF_UPDATE_OFFSET)
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
else
vn_lock(vp, LK_SHARED | LK_RETRY);
/* Compute the old and new offsets. */
oldoff = fp->f_offset;