On Mon, Jul 12, 2021 at 03:07:31PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > During a realtime grow operation, we run a single transaction for each > rt bitmap block added to the filesystem. This means that each step has > to be careful to increase sb_rblocks appropriately. > > Fix the integer overflow error in this calculation that can happen when > the extent size is very large. Found by running growfs to add a rt > volume to a filesystem formatted with a 1g rt extent size. > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > --- > fs/xfs/xfs_rtalloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > > diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c > index 8920bce4fb0a..a47d43c30283 100644 > --- a/fs/xfs/xfs_rtalloc.c > +++ b/fs/xfs/xfs_rtalloc.c > @@ -1019,7 +1019,7 @@ xfs_growfs_rt( > nsbp->sb_rbmblocks = bmbno + 1; > nsbp->sb_rblocks = > XFS_RTMIN(nrblocks, > - nsbp->sb_rbmblocks * NBBY * > + (xfs_rfsblock_t)nsbp->sb_rbmblocks * NBBY * > nsbp->sb_blocksize * nsbp->sb_rextsize); > nsbp->sb_rextents = nsbp->sb_rblocks; > do_div(nsbp->sb_rextents, nsbp->sb_rextsize); Oh, that's just nasty code. This needs a comment explaining that the cast is to avoid an overflow, otherwise someone will come along later and remove the "unnecessary" cast. Alternatively, because we do "nsbp->sb_rbmblocks = bmbno + 1;" a couple of lines above, this could be done differently without the need for a cast. Make bmbno a xfs_rfsblock_t, and simply write the code as: nsbp->sb_rblocks = min(nrblocks, (bmbno + 1) * NBBY * nsbp->sb_blocksize * nsbp->sb_rextsize); nsbp->sb_rbmblocks = bmbno + 1; Notes for future cleanup: #define XFS_RTMIN(a,b) ((a) < (b) ? (a) : (b)) Needs to die. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
