Re: [PATCH] hfs: fix array out of bounds read of array extent
From: Viacheslav Dubeyko
Date: Wed Oct 17 2018 - 19:36:21 EST
On Wed, 2018-10-17 at 15:01 -0700, Andrew Morton wrote:
> On Fri, 31 Aug 2018 15:05:38 +0100 Colin King <colin.king@xxxxxxxxxxxxx> wrote:
> > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > Currently extent and index i are both being incremented causing
> > an array out of bounds read on extent[i]. Fix this by removing
> > the extraneous increment of extent.
> > Detected by CoverityScan, CID#711541 ("Out of bounds read")
> > Fixes: d1081202f1d0 ("HFS rewrite")
> No such commit here. I assume this is 7cb74be6fd827e314f8.
> > --- a/fs/hfs/extent.c
> > +++ b/fs/hfs/extent.c
> > @@ -300,7 +300,7 @@ int hfs_free_fork(struct super_block *sb, struct hfs_cat_file *file, int type)
> > return 0;
> > blocks = 0;
> > - for (i = 0; i < 3; extent++, i++)
By the way, the hfs_free_extents() has the same logic  of for (i = 0;
i < 3; extent++, i++). It looks like that the bug is not fixed yet. Did
anyone test this patch? What's the real reproduction path for the bug?
> > + for (i = 0; i < 3; i++)
> > blocks += be16_to_cpu(extent[i].count);
> > res = hfs_free_extents(sb, extent, blocks, blocks);
> Well, that's quite the bug. Question is, why didn't anyone notice it.
> What are the runtime effects? A disk space leak, perhaps?
> I worry a bit that, given the fs was evidently working "ok", perhaps
> this error was corrected elsewhere in the code and that "fixing" this
> site will have unexpected and undesirable runtime effects. Can someone
> help me out here?