To be honest, I don't have experience.... Reference to the article " https://events19.linuxfoundation.org/wp-content/uploads/2018/07/may_be_maintainer-2.pdf"; , I tried to do some work.
1. checkpatch (√)
2. no new compile warnings (√)
3. if bug fix, verify the bug is fixed (√)
I tried some vul-samples, and the patch solved them well.
4. if new feature, feature matches documentation (×)
I try some normal samples, and there is a bug. The dir name or
filename loses a byte. You can use the attachment to check it.
I use command " mksquashfs $dir normal.sqfs -noI -noD -noF -noX" to
create the squashfs sample.
```before patch
=> ls host 0
BTRFS: superblock end 69632 is larger than device size 4096
BTRFS: superblock end 69632 is larger than device size 4096
11 hello
BTRFS: superblock end 69632 is larger than device size 4096
BTRFS: superblock end 69632 is larger than device size 4096
1 file(s), 0 dir(s)
```
```after patch
=> ls host 0
BTRFS: superblock end 69632 is larger than device size 4096
BTRFS: superblock end 69632 is larger than device size 4096
11 hell
BTRFS: superblock end 69632 is larger than device size 4096
BTRFS: superblock end 69632 is larger than device size 4096
1 file(s), 0 dir(s)
```
Tom Rini <tr...@konsulko.com> 于2022年6月7日周二 21:43写道：
> On Tue, Jun 07, 2022 at 06:00:38PM +0800, Jincheng Wang wrote:
>
> > It works well, thanks for your work.
>
> Can you please provide a Tested-by? Thanks!
>
> >
> >
> > Miquel Raynal <miquel.ray...@bootlin.com> 于2022年6月3日周五 23:26写道：
> > >
> > > Following Jincheng's report, an out-of-band write leading to arbitrary
> > > code execution is possible because on one side the squashfs logic
> > > accepts directory names up to 65535 bytes (u16), while U-Boot fs logic
> > > accepts directory names up to 255 bytes long.
> > >
> > > Prevent such an exploit from happening by capping directory name sizes
> > > to 255. Use a define for this purpose so that developers can link the
> > > limitation to its source and eventually kill it some day by dynamically
> > > allocating this array (if ever desired).
> > >
> > > Link:
> https://lore.kernel.org/all/CALO=dhfb+yboxxvr5kcsk0ifdg+e7ywko4-e+72kjbcs8jb...@mail.gmail.com
> > > Reported-by: Jincheng Wang <jc.w...@gmail.com>
> > > Signed-off-by: Miquel Raynal <miquel.ray...@bootlin.com>
> > > ---
> > >
> > > Hello Jincheng, can you please give this fix a try?
> > >
> > > Thanks!
> > > Miquèl
> > >
> > > fs/squashfs/sqfs.c | 8 +++++---
> > > include/fs.h | 4 +++-
> > > 2 files changed, 8 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> > > index b4484fa17f5..ee6ac8b3e4d 100644
> > > --- a/fs/squashfs/sqfs.c
> > > +++ b/fs/squashfs/sqfs.c
> > > @@ -976,6 +976,7 @@ int sqfs_readdir(struct fs_dir_stream *fs_dirs,
> struct fs_dirent **dentp)
> > > int i_number, offset = 0, ret;
> > > struct fs_dirent *dent;
> > > unsigned char *ipos;
> > > + u16 name_size;
> > >
> > > dirs = (struct squashfs_dir_stream *)fs_dirs;
> > > if (!dirs->size) {
> > > @@ -1058,9 +1059,10 @@ int sqfs_readdir(struct fs_dir_stream *fs_dirs,
> struct fs_dirent **dentp)
> > > return -SQFS_STOP_READDIR;
> > > }
> > >
> > > - /* Set entry name */
> > > - strncpy(dent->name, dirs->entry->name, dirs->entry->name_size
> + 1);
> > > - dent->name[dirs->entry->name_size + 1] = '\0';
> > > + /* Set entry name (capped at FS_DIRENT_NAME_LEN which is a
> U-Boot limitation) */
> > > + name_size = min_t(u16, dirs->entry->name_size,
> FS_DIRENT_NAME_LEN - 1);
> > > + strncpy(dent->name, dirs->entry->name, name_size);
> > > + dent->name[name_size] = '\0';
> > >
> > > offset = dirs->entry->name_size + 1 + SQFS_ENTRY_BASE_LENGTH;
> > > dirs->entry_count--;
> > > diff --git a/include/fs.h b/include/fs.h
> > > index b43f16a692f..2195dc172ec 100644
> > > --- a/include/fs.h
> > > +++ b/include/fs.h
> > > @@ -174,6 +174,8 @@ int fs_write(const char *filename, ulong addr,
> loff_t offset, loff_t len,
> > > #define FS_DT_REG 8 /* regular file */
> > > #define FS_DT_LNK 10 /* symbolic link */
> > >
> > > +#define FS_DIRENT_NAME_LEN 256
> > > +
> > > /**
> > > * struct fs_dirent - directory entry
> > > *
> > > @@ -194,7 +196,7 @@ struct fs_dirent {
> > > /** change_time: time of last modification */
> > > struct rtc_time change_time;
> > > /** name: file name */
> > > - char name[256];
> > > + char name[FS_DIRENT_NAME_LEN];
> > > };
> > >
> > > /* Note: fs_dir_stream should be treated as opaque to the user of fs
> layer */
> > > --
> > > 2.34.1
> > >
>
> --
> Tom
>
normal.sqfs
Description: Binary data
