On Fri, Aug 12, 2016 at 12:00:34PM +0100, Luis de Bethencourt wrote: > On 12/08/16 11:12, Salah Triki wrote: > > ag_shift is used by blockno2iaddr() to get allocation group number > > from block. If ag_shift is inconsistent with block_per_ag, an out of > > bounds allocation group may occur [1]. So add return BEFS_ERR and update > > comment and error message to reflect this change. > > > > [1] https://lkml.org/lkml/2016/8/12/42 > > > > Signed-off-by: Salah Triki <salah.triki@xxxxxxxxx> > > --- > > fs/befs/super.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/fs/befs/super.c b/fs/befs/super.c > > index 7c50025..2e3a3fd 100644 > > --- a/fs/befs/super.c > > +++ b/fs/befs/super.c > > @@ -101,10 +101,13 @@ befs_check_sb(struct super_block *sb) > > > > > > /* ag_shift also encodes the same information as blocks_per_ag in a > > - * different way, non-fatal consistency check > > + * different way as a consistency check. > > */ > > - if ((1 << befs_sb->ag_shift) != befs_sb->blocks_per_ag) > > - befs_error(sb, "ag_shift disagrees with blocks_per_ag."); > > + if ((1 << befs_sb->ag_shift) != befs_sb->blocks_per_ag) { > > + befs_error(sb, "ag_shift disagrees with blocks_per_ag. " > > + "Corruption likely."); > > + return BEFS_ERR; > > + } > > > > if (befs_sb->log_start != befs_sb->log_end || > > befs_sb->flags == BEFS_DIRTY) { > > > > Hi Salah, > > I initially also added the BEFS_ERR return for this check. I understand > it makes sense. > > But as I mentioned in the patch adding this warning [0], a correct > blocks_per_ag isn't mandatory. I noticed this because BeFS images > created by Haiku OS just set blocks_per_ag to 1. Which is clearly not > what it should be. > > The file systems created by Haiku OS can be read without issues since > sb->blocks_per_ag isn't actually used in lookups/reading file datastreams. > > This is what I get in dmesg when loading a Haiku OS image with > CONFIG_BEFS_DEBUG on: > ... > [ 196.376651] befs: (loop1): blocks_per_ag 1 > [ 196.376652] befs: (loop1): ag_shift 14 > ... > > With ag_shift of 14, blocks_per_ag should be 16,384. > > If we return BEFS_ERR, the system will refuse to mount and users won't be > able to read these Haiku OS images they could read before. Unfortunate that > Haiku OS is not using blocks_per_ag properly, but users and avoiding > regressions go first. > > Which BeFS images are you using to test the befs code? Since all the ones > I have are generated from Haiku OS, all of them have a bad blocks_per_ag. > LOL > > Maybe we should contact Haiku OS developers and ask them to write a correct > blocks_per_ag. Though we should also support images created before they fix > this. > > Sorry you spent time on this when the issue is out of our control :( > Nacked-by: Luis de Bethencourt <luisbg@xxxxxxxxxxxxxxx> > > Thanks, > Luis > > [0] https://lkml.org/lkml/2016/8/9/816 Hi Luis, > but users and avoiding regressions go first. Indeed, you are right to stress the importance of users and avoiding regressions. > Which BeFS images are you using to test the befs code? http://befs-driver.sourceforge.net/ > Maybe we should contact Haiku OS developers and ask them to write a correct > blocks_per_ag. Yes, it is a good idea. Thanks, Salah -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
