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Explicitly initialize rather than reading newly allocated UFS inodes.

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The function ffs_vgetf() is used to find or load UFS inodes into a
vnode. It first looks up the inode and if found in the cache its
vnode is returned. If it is not already in the cache, a new vnode
is allocated and its associated inode read in from the disk. The
read is done even for inodes that are being initially created.
The contents for the inode on the disk are assumed to be empty. If
the on-disk contents had been corrupted either due to a hardware
glitch or an agent deliberately trying to exploit the system, the
UFS code could panic from the unexpected partially-allocated inode.

Rather then having fsck_ffs(8) verify that all unallocated inodes
are properly empty, it is easier and quicker to add a flag to
ffs_vgetf() to indicate that the request is for a newly allocated
inode. When set, the disk read is skipped and the inode is set to
its expected empty (zero'ed out) initial state. As a side benefit,
an unneeded disk I/O is avoided.

Reported by:  Peter Holm
Sponsored by: The FreeBSD Foundation
This commit is contained in:
Kirk McKusick 2022-08-13 13:50:08 -07:00
parent 30f6269155
commit 6b9d4fbb7f
3 changed files with 33 additions and 24 deletions
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2
sys/ufs/ffs/ffs_alloc.c
View File

@ -1159,7 +1159,7 @@ ffs_valloc(struct vnode *pvp,
* return the error.
*/
if ((error = ffs_vgetf(pvp->v_mount, ino, LK_EXCLUSIVE, vpp,
FFSV_FORCEINSMQ | FFSV_REPLACE)) != 0) {
FFSV_FORCEINSMQ | FFSV_REPLACE | FFSV_NEWINODE)) != 0) {
ffs_vfree(pvp, ino, mode);
return (error);
}

1
sys/ufs/ffs/ffs_extern.h
View File

@ -132,6 +132,7 @@ int ffs_breadz(struct ufsmount *, struct vnode *, daddr_t, daddr_t, int,
doomed */
#define FFSV_FORCEINODEDEP 0x0008 /* Force allocation of inodedep, ignore
MNT_SOFTDEP */
#define FFSV_NEWINODE 0x0010 /* Newly allocated inode */
/*
* Flags to ffs_reload

54
sys/ufs/ffs/ffs_vfsops.c
View File

@ -1928,40 +1928,48 @@ ffs_vgetf(struct mount *mp,
MPASS((ffs_flags & FFSV_REPLACE) == 0);
return (0);
}
/* Read in the disk contents for the inode, copy into the inode. */
dbn = fsbtodb(fs, ino_to_fsba(fs, ino));
error = ffs_breadz(ump, ump->um_devvp, dbn, dbn, (int)fs->fs_bsize,
NULL, NULL, 0, NOCRED, 0, NULL, &bp);
if (error != 0) {
/*
* The inode does not contain anything useful, so it would
* be misleading to leave it on its hash chain. With mode
* still zero, it will be unlinked and returned to the free
* list by vput().
*/
vgone(vp);
vput(vp);
*vpp = NULL;
return (error);
}
if (I_IS_UFS1(ip))
ip->i_din1 = uma_zalloc(uma_ufs1, M_WAITOK);
else
ip->i_din2 = uma_zalloc(uma_ufs2, M_WAITOK);
if ((error = ffs_load_inode(bp, ip, fs, ino)) != 0) {
if ((ffs_flags & FFSV_NEWINODE) != 0) {
/* New inode, just zero out its contents. */
if (I_IS_UFS1(ip))
memset(ip->i_din1, 0, sizeof(struct ufs1_dinode));
else
memset(ip->i_din2, 0, sizeof(struct ufs2_dinode));
} else {
/* Read the disk contents for the inode, copy into the inode. */
dbn = fsbtodb(fs, ino_to_fsba(fs, ino));
error = ffs_breadz(ump, ump->um_devvp, dbn, dbn,
(int)fs->fs_bsize, NULL, NULL, 0, NOCRED, 0, NULL, &bp);
if (error != 0) {
/*
* The inode does not contain anything useful, so it
* would be misleading to leave it on its hash chain.
* With mode still zero, it will be unlinked and
* returned to the free list by vput().
*/
vgone(vp);
vput(vp);
*vpp = NULL;
return (error);
}
if ((error = ffs_load_inode(bp, ip, fs, ino)) != 0) {
bqrelse(bp);
vgone(vp);
vput(vp);
*vpp = NULL;
return (error);
}
bqrelse(bp);
vgone(vp);
vput(vp);
*vpp = NULL;
return (error);
}
if (DOINGSOFTDEP(vp) && (!fs->fs_ronly ||
(ffs_flags & FFSV_FORCEINODEDEP) != 0))
softdep_load_inodeblock(ip);
else
ip->i_effnlink = ip->i_nlink;
bqrelse(bp);
/*
* Initialize the vnode from the inode, check for aliases.