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geom_label: Partially reinstate old sysinstall(8) workaround

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This partially reverts commit af433832f7.
Since such bogus disklabels still exist in the wild, we now probe for a
disklabel to decide whether to ignore the UFS partition or not; if there
is a label then we use the old behaviour, and if there isn't one then we
use the new behaviour.

Reviewed by:	cy, mckusick
Differential Revision:	https://reviews.freebsd.org/D31068
This commit is contained in:
Jessica Clarke 2021-07-21 02:24:55 +01:00
parent b684d812fc
commit e77ef47d36
1 changed files with 79 additions and 0 deletions
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79
sys/geom/label/g_label_ufs.c
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@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/disklabel.h>
#include <sys/malloc.h>
#include <sys/vnode.h>
@ -48,6 +49,81 @@ __FBSDID("$FreeBSD$");
#define G_LABEL_UFS_VOLUME 0
#define G_LABEL_UFS_ID 1
/*
* G_LABEL_UFS_CMP returns true if difference between provider mediasize
* and filesystem size is less than G_LABEL_UFS_MAXDIFF sectors
*/
#define G_LABEL_UFS_CMP(prov, fsys, size) \
( abs( ((fsys)->size) - ( (prov)->mediasize / (fsys)->fs_fsize )) \
< G_LABEL_UFS_MAXDIFF )
#define G_LABEL_UFS_MAXDIFF 0x100
/*
* For providers that look like disklabels we need to check if the file system
* size is almost equal to the provider's size, because sysinstall(8) used to
* bogusly put the first partition at offset 0 instead of 16, and glabel/ufs
* would find a file system on the slice instead of the partition.
*
* In addition, media size can be a bit bigger than file system size. For
* instance, mkuzip can append bytes to align data to large sector size (it
* improves compression rates).
*/
static bool
g_label_ufs_ignore_bsdlabel_slice(struct g_consumer *cp,
struct fs *fs)
{
struct g_provider *pp;
u_char *buf;
uint32_t magic1, magic2;
int error;
pp = cp->provider;
/*
* If the expected provider size for the filesystem matches the
* real provider size then don't ignore this filesystem.
*/
if (G_LABEL_UFS_CMP(pp, fs, fs_providersize))
return (false);
/*
* If the filesystem size matches the real provider size then
* don't ignore this filesystem.
*/
if (fs->fs_magic == FS_UFS1_MAGIC ?
G_LABEL_UFS_CMP(pp, fs, fs_old_size) :
G_LABEL_UFS_CMP(pp, fs, fs_size))
return (false);
/*
* Provider is bigger than expected; probe to see if there's a
* disklabel. Adapted from g_part_bsd_probe.
*/
/* Check if the superblock overlaps where the disklabel lives. */
if (fs->fs_sblockloc < pp->sectorsize * 2)
return (false);
/* Sanity-check the provider. */
if (pp->sectorsize < sizeof(struct disklabel) ||
pp->mediasize < BBSIZE)
return (false);
if (BBSIZE % pp->sectorsize)
return (false);
/* Check that there's a disklabel. */
buf = g_read_data(cp, pp->sectorsize, pp->sectorsize, &error);
if (buf == NULL)
return (false);
magic1 = le32dec(buf + 0);
magic2 = le32dec(buf + 132);
g_free(buf);
if (magic1 == DISKMAGIC && magic2 == DISKMAGIC)
return (true);
return (false);
}
/*
* Try to find a superblock on the provider. If successful, look for a volume
* label and create an appropriate provider based on that.
@ -78,6 +154,9 @@ g_label_ufs_taste_common(struct g_consumer *cp, char *label, size_t size, int wh
} else {
goto out;
}
/* Check if this should be ignored for compatibility. */
if (g_label_ufs_ignore_bsdlabel_slice(cp, fs))
goto out;
G_LABEL_DEBUG(1, "%s file system detected on %s.",
fs->fs_magic == FS_UFS1_MAGIC ? "UFS1" : "UFS2", pp->name);
switch (what) {