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Stop segfaulting on unmount error case #12804

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Nov 30, 2021
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Stop segfaulting on unmount error case #12804

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10 changes: 7 additions & 3 deletions lib/libzfs/libzfs_mount.c
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Original file line number Diff line number Diff line change
Expand Up @@ -595,9 +595,13 @@ unmount_one(zfs_handle_t *zhp, const char *mountpoint, int flags)
default:
libzfs_err = EZFS_UMOUNTFAILED;
}
return (zfs_error_fmt(zhp->zfs_hdl, libzfs_err,
dgettext(TEXT_DOMAIN, "cannot unmount '%s'"),
mountpoint));
if (zhp) {
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If zhp == NULL invoking unmount_one doesn't make sense at all. Most likely null value is injected from

zfs/lib/libzfs/libzfs_mount.c

Line 1636 in d41856a

if (unmount_one(sets[i].dataset, sets[i].mountpoint,
and the if-guard should go there, much like it is done few lines below:

zfs/lib/libzfs/libzfs_mount.c

Line 1642 in d41856a

if (sets[i].dataset)

and

zfs/lib/libzfs/libzfs_mount.c

Line 1652 in d41856a

if (sets[i].dataset)

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I mostly put the guard in there because of the comment at

zfs/lib/libzfs/libzfs_mount.c

Line 1599 in d41856a

/*
suggesting that sometimes calling with a NULL was deliberately permitted - and if you look, do_unmount on Linux doesn't actually use the zhp arg anywhere, so it could have something reasonable happen when called there.

I don't particularly care either way, I just went for the option that changed less behavior.

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You're right, Rich. Indeed zhp is used in neither of OS-specific implementations, what really matters is the mountpoint. Quite a surprise to be honest :)

return (zfs_error_fmt(zhp->zfs_hdl, libzfs_err,
dgettext(TEXT_DOMAIN, "cannot unmount '%s'"),
mountpoint));
} else {
return (-1);
}
}

return (0);
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