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    SubjectRe: [PATCH 061/190] Revert "xen/grant-table: remove multiple BUG_ON on gnttab_interface"
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    On 21.04.21 14:58, Greg Kroah-Hartman wrote:
    > This reverts commit d6bd6cf9feb81737f9f64d2c1acf98fdaacebad1.
    >
    > Commits from @umn.edu addresses have been found to be submitted in "bad
    > faith" to try to test the kernel community's ability to review "known
    > malicious" changes. The result of these submissions can be found in a
    > paper published at the 42nd IEEE Symposium on Security and Privacy
    > entitled, "Open Source Insecurity: Stealthily Introducing
    > Vulnerabilities via Hypocrite Commits" written by Qiushi Wu (University
    > of Minnesota) and Kangjie Lu (University of Minnesota).
    >
    > Because of this, all submissions from this group must be reverted from
    > the kernel tree and will need to be re-reviewed again to determine if
    > they actually are a valid fix. Until that work is complete, remove this
    > change to ensure that no problems are being introduced into the
    > codebase.
    >
    > Cc: Aditya Pakki <pakki001@umn.edu>
    > Cc: Juergen Gross <jgross@suse.com>
    > Cc: Juergen Gross <jgross@suse.com>
    > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    The reverted patch didn't introduce any issue. I have verified that the
    BUG_ON()s are really impossible to trigger, and even if they would have
    been triggering, they'd be now replaced by NULL dereferences.

    So I believe you can just drop this revert.


    Juergen

    > ---
    > drivers/xen/grant-table.c | 4 ++++
    > 1 file changed, 4 insertions(+)
    >
    > diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
    > index 3729bea0c989..5065d36c602e 100644
    > --- a/drivers/xen/grant-table.c
    > +++ b/drivers/xen/grant-table.c
    > @@ -663,6 +663,7 @@ static int grow_gnttab_list(unsigned int more_frames)
    > unsigned int nr_glist_frames, new_nr_glist_frames;
    > unsigned int grefs_per_frame;
    >
    > + BUG_ON(gnttab_interface == NULL);
    > grefs_per_frame = gnttab_interface->grefs_per_grant_frame;
    >
    > new_nr_grant_frames = nr_grant_frames + more_frames;
    > @@ -1281,6 +1282,7 @@ EXPORT_SYMBOL_GPL(gnttab_unmap_refs_sync);
    >
    > static unsigned int nr_status_frames(unsigned int nr_grant_frames)
    > {
    > + BUG_ON(gnttab_interface == NULL);
    > return gnttab_frames(nr_grant_frames, SPP);
    > }
    >
    > @@ -1508,6 +1510,7 @@ static int gnttab_expand(unsigned int req_entries)
    > int rc;
    > unsigned int cur, extra;
    >
    > + BUG_ON(gnttab_interface == NULL);
    > cur = nr_grant_frames;
    > extra = ((req_entries + gnttab_interface->grefs_per_grant_frame - 1) /
    > gnttab_interface->grefs_per_grant_frame);
    > @@ -1542,6 +1545,7 @@ int gnttab_init(void)
    > /* Determine the maximum number of frames required for the
    > * grant reference free list on the current hypervisor.
    > */
    > + BUG_ON(gnttab_interface == NULL);
    > max_nr_glist_frames = (max_nr_grant_frames *
    > gnttab_interface->grefs_per_grant_frame / RPP);
    >
    >

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