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dm: fix dropped return code from dm_get_bdev_for_ioctl

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dm_get_bdev_for_ioctl()'s return of 0 or 1 must be the result from
prepare_ioctl (1 means the ioctl was issued to a partition, 0 means it
wasn't).  Unfortunately commit 519049afea ("dm: use blkdev_get rather
than bdgrab when issuing pass-through ioctl") reused the variable 'r'
to store the return from blkdev_get() that follows prepare_ioctl()
-- whereby dropping prepare_ioctl()'s result on the floor.

This can lead to an ioctl or persistent reservation being issued to a
partition going unnoticed, which implies the extra permission check for
CAP_SYS_RAWIO is skipped.

Fix this by using a different variable to store blkdev_get()'s return.

Fixes: 519049afea ("dm: use blkdev_get rather than bdgrab when issuing pass-through ioctl")
Reported-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2018-03-29 23:31:32 -04:00
parent e457edf0b2
commit da5dadb4f1
1 changed files with 5 additions and 3 deletions
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8
drivers/md/dm.c
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@ -466,7 +466,7 @@ static int dm_get_bdev_for_ioctl(struct mapped_device *md,
{
struct dm_target *tgt;
struct dm_table *map;
int srcu_idx, r;
int srcu_idx, r, r2;
retry:
r = -ENOTTY;
@ -492,9 +492,11 @@ retry:
goto out;
bdgrab(*bdev);
r = blkdev_get(*bdev, *mode, _dm_claim_ptr);
if (r < 0)
r2 = blkdev_get(*bdev, *mode, _dm_claim_ptr);
if (r2 < 0) {
r = r2;
goto out;
}
dm_put_live_table(md, srcu_idx);
return r;