Messages in this thread | | | Subject | Re: [Cluster-devel] [PATCH] gfs2: gfs2_read_sb: put gfs2_assert inside the loop | From | Andrew Price <> | Date | Mon, 5 Oct 2020 14:23:03 +0100 |
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On 03/10/2020 07:31, Fox Chen wrote: > for (x = 2;; x++) { > ... > gfs2_assert(sdp, x <= GFS2_MAX_META_HEIGHT); <--- after > ... > if (d != sdp->sd_heightsize[x - 1] || m) > break; > sdp->sd_heightsize[x] = space; > } > > sdp->sd_max_height = x > gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT) <--- before > > Before this patch, gfs2_assert is put outside of the loop of > sdp->sd_heightsize[x] calculation. When something goes wrong,
So this looks related to one of the recent syzbot reports, where the "something goes wrong" is the block size in the on-disk superblock was zeroed and that leads eventually to this out-of-bounds write. The correct fix in that case would be to add a validity check for the block size in gfs2_check_sb().
Andy
> x exceeds the size of GFS2_MAX_META_HEIGHT, it may already crash inside > the loop when > > sdp->sd_heightsize[x] = space > > tries to reach the out-of-bound > location, gfs2_assert won't help here. > > This patch fixes this by moving gfs2_assert into the loop. > We will check x value each time to see if it exceeds GFS2_MAX_META_HEIGHT. > > Signed-off-by: Fox Chen <foxhlchen@gmail.com> > --- > fs/gfs2/ops_fstype.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c > index 6d18d2c91add..6cc32e3010f2 100644 > --- a/fs/gfs2/ops_fstype.c > +++ b/fs/gfs2/ops_fstype.c > @@ -333,6 +333,7 @@ static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent) > u64 space, d; > u32 m; > > + gfs2_assert(sdp, x <= GFS2_MAX_META_HEIGHT); > space = sdp->sd_heightsize[x - 1] * sdp->sd_inptrs; > d = space; > m = do_div(d, sdp->sd_inptrs); > @@ -343,7 +344,6 @@ static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent) > } > sdp->sd_max_height = x; > sdp->sd_heightsize[x] = ~0; > - gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT); > > sdp->sd_max_dents_per_leaf = (sdp->sd_sb.sb_bsize - > sizeof(struct gfs2_leaf)) / >
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