Messages in this thread | | | Date | Fri, 12 Aug 2016 08:26:51 +0100 | From | Salah Triki <> | Subject | Re: [PATCH 1/4] befs: check allocation_group number before use |
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On Thu, Aug 11, 2016 at 11:56:16AM +0100, Luis de Bethencourt wrote: > On 10/08/16 23:12, Salah Triki wrote: > > Check that the allocation group number is not greater or equal to the > > number of allocations group in the file system and return BEF_ERR in the > > case of error. > > > > Signed-off-by: Salah Triki <salah.triki@gmail.com> > > --- > > fs/befs/befs.h | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/fs/befs/befs.h b/fs/befs/befs.h > > index 55f3ea2..6daf4c4 100644 > > --- a/fs/befs/befs.h > > +++ b/fs/befs/befs.h > > @@ -121,6 +121,11 @@ BEFS_I(const struct inode *inode) > > static inline befs_blocknr_t > > iaddr2blockno(struct super_block *sb, const befs_inode_addr *iaddr) > > { > > + if (iaddr->allocation_group >= BEFS_SB(sb)->num_ags) { > > + befs_error(sb, "BEFS: Invalid allocation group %u, max is %u", > > + iaddr->allocation_group, BEFS_SB(sb)->num_ags); > > + return BEFS_ERR; > > + } > > return ((iaddr->allocation_group << BEFS_SB(sb)->ag_shift) + > > iaddr->start); > > } > > > > Hi Salah, > > To understand why would we check for this. When can this error happen? I mean, > when can iaddr2blockno() be called with an out of bounds allocation group? > > Thanks, > Luis
Hi Luis,
allocation group number is set to blockno >> BEFS_SB(sb)->ag_shift by blockno2iaddr(), so if ag_shift is not valid, an out of bound may occur. By now, thanx to your question ;), I think it's better to check the validity of ag_shift when the superblock is loaded.
Nack.
Thanx for the question :) Salah
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