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cluster_write(): do not access buffer after it is released

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The issue was reported by
Alexander Lochmann <alexander.lochmann@tu-dortmund.de>,
who found the problem by performing lock analysis using LockDoc,
see https://doi.org/10.1145/3302424.3303948.

Reviewed by:	mckusick
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D31780
This commit is contained in:
Konstantin Belousov 2021-09-02 07:04:23 +03:00
parent 6352bbf7be
commit 5cc82c563e
1 changed files with 8 additions and 3 deletions
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11
sys/kern/vfs_cluster.c
View File

@ -646,7 +646,7 @@ void
cluster_write(struct vnode *vp, struct vn_clusterw *vnc, struct buf *bp,
u_quad_t filesize, int seqcount, int gbflags)
{
daddr_t lbn;
daddr_t lbn, pbn;
int maxclen, cursize;
int lblocksize;
int async;
@ -753,14 +753,16 @@ cluster_write(struct vnode *vp, struct vn_clusterw *vnc, struct buf *bp,
bp->b_blkno == bp->b_lblkno &&
(VOP_BMAP(vp, lbn, NULL, &bp->b_blkno, &maxclen,
NULL) != 0 || bp->b_blkno == -1)) {
pbn = bp->b_blkno;
bawrite(bp);
vnc->v_clen = 0;
vnc->v_lasta = bp->b_blkno;
vnc->v_lasta = pbn;
vnc->v_cstart = lbn + 1;
vnc->v_lastw = lbn;
return;
}
vnc->v_clen = maxclen;
pbn = bp->b_blkno;
if (!async && maxclen == 0) { /* I/O not contiguous */
vnc->v_cstart = lbn + 1;
bawrite(bp);
@ -774,6 +776,7 @@ cluster_write(struct vnode *vp, struct vn_clusterw *vnc, struct buf *bp,
* are operating sequentially, otherwise let the buf or
* update daemon handle it.
*/
pbn = bp->b_blkno;
bdwrite(bp);
if (seqcount > 1) {
cluster_wbuild_wb(vp, lblocksize, vnc->v_cstart,
@ -785,15 +788,17 @@ cluster_write(struct vnode *vp, struct vn_clusterw *vnc, struct buf *bp,
/*
* We are low on memory, get it going NOW
*/
pbn = bp->b_blkno;
bawrite(bp);
} else {
/*
* In the middle of a cluster, so just delay the I/O for now.
*/
pbn = bp->b_blkno;
bdwrite(bp);
}
vnc->v_lastw = lbn;
vnc->v_lasta = bp->b_blkno;
vnc->v_lasta = pbn;
}
/*