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msdosfs: zero tail of the last block on truncation for VREG vnodes as well.

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Despite the call to vtruncbuf() from detrunc(), which results in
zeroing part of the partial page after EOF, there still is a
possibility to retain the stale data which is revived on file
enlargement.  If the filesystem block size is greater than the page
size, partial block might keep other after-EOF pages wired and they
get reused then.  Fix it by zeroing whole part of the partial buffer
after EOF, not relying on vnode_pager_setsize().

PR:	236977
Reported by:	asomers
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2019-04-03 17:02:18 +00:00
parent 2b9dde098f
commit c973ee9e06
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=345847
1 changed files with 14 additions and 12 deletions
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26
sys/fs/msdosfs/msdosfs_denode.c
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@ -405,19 +405,21 @@ detrunc(struct denode *dep, u_long length, int flags, struct ucred *cred)
bn = cntobn(pmp, eofentry);
error = bread(pmp->pm_devvp, bn, pmp->pm_bpcluster,
NOCRED, &bp);
if (error) {
brelse(bp);
#ifdef MSDOSFS_DEBUG
printf("detrunc(): bread fails %d\n", error);
#endif
return (error);
}
memset(bp->b_data + boff, 0, pmp->pm_bpcluster - boff);
if (flags & IO_SYNC)
bwrite(bp);
else
bdwrite(bp);
} else {
error = bread(DETOV(dep), de_cluster(pmp, length),
pmp->pm_bpcluster, cred, &bp);
}
if (error) {
#ifdef MSDOSFS_DEBUG
printf("detrunc(): bread fails %d\n", error);
#endif
return (error);
}
memset(bp->b_data + boff, 0, pmp->pm_bpcluster - boff);
if ((flags & IO_SYNC) != 0)
bwrite(bp);
else
bdwrite(bp);
}
/*