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Date: Thu, 20 Feb 2014 12:07:30 +0100 (CET)
From: Lukáš Czerner <lczerner@...hat.com>
To: "Darrick J. Wong" <darrick.wong@...cle.com>
cc: linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH] e2fsprogs: make ext2fs_free() to set the pointer to
NULL
On Wed, 19 Feb 2014, Darrick J. Wong wrote:
> Date: Wed, 19 Feb 2014 15:39:17 -0800
> From: Darrick J. Wong <darrick.wong@...cle.com>
> To: Lukas Czerner <lczerner@...hat.com>
> Cc: linux-ext4@...r.kernel.org, tytso@....edu
> Subject: Re: [PATCH] e2fsprogs: make ext2fs_free() to set the pointer to NULL
>
> On Wed, Feb 19, 2014 at 12:48:16PM +0100, Lukas Czerner wrote:
> > Currently someone uses ext2fs_free() to free the ext2_filsys structure,
> > he is also responsible to set the pointer to that structure to NULL,
> > because ext2fs_free() is not able to do that.
> >
> > This however is in contrast with ext2fs_free_mem() which requires as an
> > argument pointer to the pointer and it will in fact set the pointer to
> > NULL for us. This is probably the reason why majority of places where we
> > use ext2fs_free() does not set the pointer to NULL afterwards.
> >
> > Fix this by changing function ext2fs_free() so that it'll require
> > pointer to the ext2_filsys as an argument and will be able to set the
> > pointer to NULL for us.
> >
> > I do not currently have any way to trigger the issue in recent
> > e2fsprogs. Part of the reason is that there are some fixes which just
> > obfuscates the real problem (for example
> > 7ff040f30f0ff3bf5e2c832da3cb577e00a52d60) and the other part might be
> > just coincidence.
> >
> > I was however able to reproduce this with e2fsprogs 1.42.9 using the
> > image in bug https://bugzilla.redhat.com/show_bug.cgi?id=997982. With
> > this patch it fixes it. However I am not sure why it got fixed in the
> > recent e2fsprogs since git bisect lands into the merge commit - however
> > I think it's just a coincidence rather than targeted fix.
> >
> > Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> > ---
> > e2fsck/journal.c | 2 +-
> > e2fsck/unix.c | 12 ++++--------
> > lib/ext2fs/closefs.c | 2 +-
> > lib/ext2fs/dupfs.c | 2 +-
> > lib/ext2fs/ext2fs.h | 2 +-
> > lib/ext2fs/freefs.c | 10 ++++++++--
> > lib/ext2fs/initialize.c | 2 +-
> > lib/ext2fs/openfs.c | 7 +++----
> > misc/tune2fs.c | 2 +-
> > resize/online.c | 2 +-
> > resize/resize2fs.c | 4 ++--
> > 11 files changed, 24 insertions(+), 23 deletions(-)
> >
> > diff --git a/e2fsck/journal.c b/e2fsck/journal.c
> > index a7b1150..ef964a0 100644
> > --- a/e2fsck/journal.c
> > +++ b/e2fsck/journal.c
> > @@ -965,7 +965,7 @@ errcode_t e2fsck_run_ext3_journal(e2fsck_t ctx)
> > kbytes_written = stats->bytes_written >> 10;
> >
> > ext2fs_mmp_stop(ctx->fs);
> > - ext2fs_free(ctx->fs);
> > + ext2fs_free(&ctx->fs);
> > retval = ext2fs_open(ctx->filesystem_name, EXT2_FLAG_RW,
> > ctx->superblock, blocksize, io_ptr,
> > &ctx->fs);
> > diff --git a/e2fsck/unix.c b/e2fsck/unix.c
> > index 429f1cd..b4d23de 100644
> > --- a/e2fsck/unix.c
> > +++ b/e2fsck/unix.c
> > @@ -1051,10 +1051,8 @@ static errcode_t try_open_fs(e2fsck_t ctx, int flags, io_manager io_ptr,
> > int blocksize;
> > for (blocksize = EXT2_MIN_BLOCK_SIZE;
> > blocksize <= EXT2_MAX_BLOCK_SIZE; blocksize *= 2) {
> > - if (*ret_fs) {
> > - ext2fs_free(*ret_fs);
> > - *ret_fs = NULL;
> > - }
> > + if (*ret_fs)
> > + ext2fs_free(ret_fs);
> > retval = ext2fs_open2(ctx->filesystem_name,
> > ctx->io_options, flags,
> > ctx->superblock, blocksize,
> > @@ -1292,10 +1290,8 @@ restart:
> > retval = retval2;
> > goto failure;
> > }
> > - if (fs->flags & EXT2_FLAG_NOFREE_ON_ERROR) {
> > - ext2fs_free(fs);
> > - fs = NULL;
> > - }
> > + if (fs->flags & EXT2_FLAG_NOFREE_ON_ERROR)
> > + ext2fs_free(&fs);
> > if (!fs || (fs->group_desc_count > 1)) {
> > log_out(ctx, _("%s: %s trying backup blocks...\n"),
> > ctx->program_name,
> > diff --git a/lib/ext2fs/closefs.c b/lib/ext2fs/closefs.c
> > index c2eaec1..b0e515d 100644
> > --- a/lib/ext2fs/closefs.c
> > +++ b/lib/ext2fs/closefs.c
> > @@ -490,7 +490,7 @@ errcode_t ext2fs_close2(ext2_filsys fs, int flags)
> > if (retval)
> > return retval;
> >
> > - ext2fs_free(fs);
> > + ext2fs_free(&fs);
>
> Doesn't this change also require ext2fs_close2() take a (ext2_filsys *)?
>From the quick look it seems that users of ext2fs_close2 (or
ext2fs_close) are doing the right thing when needed and setting the
pointer to NULL afterwards. But i will need careful auditing as
well. Thanks for pointing that out.
>
> If you're going to make an ABI change, you might as well fix the get/free_mem
> ABIs to take (void **) since that's what they've been doing all along anyway.
See my response to Ted, I'd like to avoid ABI change.
Thanks!
-Lukas
>
> --D
>
> > return 0;
> > }
> >
> > diff --git a/lib/ext2fs/dupfs.c b/lib/ext2fs/dupfs.c
> > index 02721e1..7568d89 100644
> > --- a/lib/ext2fs/dupfs.c
> > +++ b/lib/ext2fs/dupfs.c
> > @@ -115,7 +115,7 @@ errcode_t ext2fs_dup_handle(ext2_filsys src, ext2_filsys *dest)
> > *dest = fs;
> > return 0;
> > errout:
> > - ext2fs_free(fs);
> > + ext2fs_free(&fs);
> > return retval;
> >
> > }
> > diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> > index 7f7fd1f..a084888 100644
> > --- a/lib/ext2fs/ext2fs.h
> > +++ b/lib/ext2fs/ext2fs.h
> > @@ -1213,7 +1213,7 @@ extern char *ext2fs_find_block_device(dev_t device);
> > extern errcode_t ext2fs_sync_device(int fd, int flushb);
> >
> > /* freefs.c */
> > -extern void ext2fs_free(ext2_filsys fs);
> > +extern void ext2fs_free(ext2_filsys *fs);
> > extern void ext2fs_free_dblist(ext2_dblist dblist);
> > extern void ext2fs_badblocks_list_free(ext2_badblocks_list bb);
> > extern void ext2fs_u32_list_free(ext2_u32_list bb);
> > diff --git a/lib/ext2fs/freefs.c b/lib/ext2fs/freefs.c
> > index 89a157b..be7c677 100644
> > --- a/lib/ext2fs/freefs.c
> > +++ b/lib/ext2fs/freefs.c
> > @@ -18,8 +18,14 @@
> > #include "ext2_fs.h"
> > #include "ext2fsP.h"
> >
> > -void ext2fs_free(ext2_filsys fs)
> > +/*
> > + * Free ext2_filsys. The 'fs_ptr' arg must point to a ext2_filsys
> > + * which is the pointer to struct_ext2_filsys.
> > + */
> > +void ext2fs_free(ext2_filsys *fs_ptr)
> > {
> > + ext2_filsys fs = *fs_ptr;
> > +
> > if (!fs || (fs->magic != EXT2_ET_MAGIC_EXT2FS_FILSYS))
> > return;
> > if (fs->image_io != fs->io) {
> > @@ -61,7 +67,7 @@ void ext2fs_free(ext2_filsys fs)
> >
> > fs->magic = 0;
> >
> > - ext2fs_free_mem(&fs);
> > + ext2fs_free_mem(fs_ptr);
> > }
> >
> > /*
> > diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
> > index 75fbf8e..72ff090 100644
> > --- a/lib/ext2fs/initialize.c
> > +++ b/lib/ext2fs/initialize.c
> > @@ -530,6 +530,6 @@ ipg_retry:
> > return 0;
> > cleanup:
> > free(buf);
> > - ext2fs_free(fs);
> > + ext2fs_free(&fs);
> > return retval;
> > }
> > diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
> > index aba8a50..6a49083 100644
> > --- a/lib/ext2fs/openfs.c
> > +++ b/lib/ext2fs/openfs.c
> > @@ -476,10 +476,9 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
> >
> > return 0;
> > cleanup:
> > - if (flags & EXT2_FLAG_NOFREE_ON_ERROR)
> > - *ret_fs = fs;
> > - else
> > - ext2fs_free(fs);
> > + if (!(flags & EXT2_FLAG_NOFREE_ON_ERROR))
> > + ext2fs_free(&fs);
> > + *ret_fs = fs;
> > return retval;
> > }
> >
> > diff --git a/misc/tune2fs.c b/misc/tune2fs.c
> > index 8ff47d2..5a3f6db 100644
> > --- a/misc/tune2fs.c
> > +++ b/misc/tune2fs.c
> > @@ -2471,7 +2471,7 @@ retry_open:
> > fprintf(stderr, "%s",
> > _("Couldn't find valid filesystem superblock.\n"));
> >
> > - ext2fs_free(fs);
> > + ext2fs_free(&fs);
> > exit(1);
> > }
> > fs->default_bitmap_type = EXT2FS_BMAP64_RBTREE;
> > diff --git a/resize/online.c b/resize/online.c
> > index 46d86b0..afd5bb6 100644
> > --- a/resize/online.c
> > +++ b/resize/online.c
> > @@ -290,7 +290,7 @@ errcode_t online_resize_fs(ext2_filsys fs, const char *mtpt,
> > }
> > }
> >
> > - ext2fs_free(new_fs);
> > + ext2fs_free(&new_fs);
> > close(fd);
> >
> > return 0;
> > diff --git a/resize/resize2fs.c b/resize/resize2fs.c
> > index 498cf99..6f19528 100644
> > --- a/resize/resize2fs.c
> > +++ b/resize/resize2fs.c
> > @@ -208,7 +208,7 @@ errcode_t resize_fs(ext2_filsys fs, blk64_t *new_size, int flags,
> >
> > rfs->flags = flags;
> >
> > - ext2fs_free(rfs->old_fs);
> > + ext2fs_free(&rfs->old_fs);
> > if (rfs->itable_buf)
> > ext2fs_free_mem(&rfs->itable_buf);
> > if (rfs->reserve_blocks)
> > @@ -221,7 +221,7 @@ errcode_t resize_fs(ext2_filsys fs, blk64_t *new_size, int flags,
> >
> > errout:
> > if (rfs->new_fs)
> > - ext2fs_free(rfs->new_fs);
> > + ext2fs_free(&rfs->new_fs);
> > if (rfs->itable_buf)
> > ext2fs_free_mem(&rfs->itable_buf);
> > ext2fs_free_mem(&rfs);
> > --
> > 1.8.3.1
> >
> > --
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>
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