Re: [PATCH -next 1/2] ext4: fix potential memory leak in ext4_fc_record_regions()

[Damien Guibouret]

Hello,

Le 20/09/2022 à 03:07, yebin a écrit :
> On 2022/9/20 2:40, Damien Guibouret wrote:
> > Hello,
> >
> > Le 19/09/2022 à 16:40, Ye Bin a écrit :
> > > As krealloc may return NULL, in this case 'state->fc_regions' may not be
> > > freed by krealloc, but 'state->fc_regions' already set NULL. Then will
> > > lead to 'state->fc_regions' memory leak.
> > >
> > > Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
> > > ---
> > >   fs/ext4/fast_commit.c | 14 ++++++++------
> > >   1 file changed, 8 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> > > index 9217a588afd1..cc8c8db075ba 100644
> > > --- a/fs/ext4/fast_commit.c
> > > +++ b/fs/ext4/fast_commit.c
> > > @@ -1677,15 +1677,17 @@ int ext4_fc_record_regions(struct super_block 
> > > *sb, int ino,
> > >       if (replay && state->fc_regions_used != state->fc_regions_valid)
> > >           state->fc_regions_used = state->fc_regions_valid;
> > >       if (state->fc_regions_used == state->fc_regions_size) {
> > > +        struct ext4_fc_alloc_region *fc_regions;
> > > +
> > >           state->fc_regions_size +=
> > >               EXT4_FC_REPLAY_REALLOC_INCREMENT;
> > > -        state->fc_regions = krealloc(
> > > -                    state->fc_regions,
> > > -                    state->fc_regions_size *
> > > -                    sizeof(struct ext4_fc_alloc_region),
> > > -                    GFP_KERNEL);
> > > -        if (!state->fc_regions)
> > > +        fc_regions = krealloc(state->fc_regions,
> > > +                      state->fc_regions_size *
> > > +                      sizeof(struct ext4_fc_alloc_region),
> > > +                      GFP_KERNEL);
> > > +        if (!fc_regions)
> >
> > Would it not be safer to restore state->fc_regions_size to its 
> > previous value in that case to keep consistency between size value and 
> > allocated size (or to update state->fc_regions_size only after 
> > allocation as it is done in second part of this patch) ?
> Actually, If   'ext4_fc_record_regions()' return -ENOMEM, then will stop 
> replay journal.
> 'state->fc_regions_size' will not be used any more, so it's safe.

There are at least two calls in ext4_ext_clear_bb (ext4/extents.c) that 
do not check for return code of ext4_fc_record_regions. But perhaps 
these are these calls that should be fixed.

> > >               return -ENOMEM;
> > > +        state->fc_regions = fc_regions;
> > >       }
> > >       region = &state->fc_regions[state->fc_regions_used++];
> > >       region->ino = ino;

Regards,

Damien