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| author | Kees Cook <keescook@chromium.org> | 2018-08-03 12:52:58 -0700 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2018-08-04 07:53:46 -0700 |
| commit | 961b33c244e5ba1543ae26270a1ba29f29c2db83 (patch) | |
| tree | b2e0bdb72b4e43774aa1264c9bf9f3df1e8cb2d8 /fs/jfs | |
| parent | 7daf201d7fe8334e2d2364d4e8ed3394ec9af819 (diff) | |
| download | lwn-961b33c244e5ba1543ae26270a1ba29f29c2db83.tar.gz lwn-961b33c244e5ba1543ae26270a1ba29f29c2db83.zip | |
jfs: Fix usercopy whitelist for inline inode data
Bart Massey reported what turned out to be a usercopy whitelist false
positive in JFS when symlink contents exceeded 128 bytes. The inline
inode data (i_inline) is actually designed to overflow into the "extended
area" following it (i_inline_ea) when needed. So the whitelist needed to
be expanded to include both i_inline and i_inline_ea (the whole size
of which is calculated internally using IDATASIZE, 256, instead of
sizeof(i_inline), 128).
$ cd /mnt/jfs
$ touch $(perl -e 'print "B" x 250')
$ ln -s B* b
$ ls -l >/dev/null
[ 249.436410] Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLUB object 'jfs_ip' (offset 616, size 250)!
Reported-by: Bart Massey <bart.massey@gmail.com>
Fixes: 8d2704d382a9 ("jfs: Define usercopy region in jfs_ip slab cache")
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: jfs-discussion@lists.sourceforge.net
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'fs/jfs')
| -rw-r--r-- | fs/jfs/jfs_dinode.h | 7 | ||||
| -rw-r--r-- | fs/jfs/jfs_incore.h | 1 | ||||
| -rw-r--r-- | fs/jfs/super.c | 3 |
3 files changed, 9 insertions, 2 deletions
diff --git a/fs/jfs/jfs_dinode.h b/fs/jfs/jfs_dinode.h index 395c4c0d0f06..1682a87c00b2 100644 --- a/fs/jfs/jfs_dinode.h +++ b/fs/jfs/jfs_dinode.h @@ -115,6 +115,13 @@ struct dinode { dxd_t _dxd; /* 16: */ union { __le32 _rdev; /* 4: */ + /* + * The fast symlink area + * is expected to overflow + * into _inlineea when + * needed (which will clear + * INLINEEA). + */ u8 _fastsymlink[128]; } _u; u8 _inlineea[128]; diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h index 1f26d1910409..9940a1e04cbf 100644 --- a/fs/jfs/jfs_incore.h +++ b/fs/jfs/jfs_incore.h @@ -87,6 +87,7 @@ struct jfs_inode_info { struct { unchar _unused[16]; /* 16: */ dxd_t _dxd; /* 16: */ + /* _inline may overflow into _inline_ea when needed */ unchar _inline[128]; /* 128: inline symlink */ /* _inline_ea may overlay the last part of * file._xtroot if maxentry = XTROOTINITSLOT diff --git a/fs/jfs/super.c b/fs/jfs/super.c index 1b9264fd54b6..f08571433aba 100644 --- a/fs/jfs/super.c +++ b/fs/jfs/super.c @@ -967,8 +967,7 @@ static int __init init_jfs_fs(void) jfs_inode_cachep = kmem_cache_create_usercopy("jfs_ip", sizeof(struct jfs_inode_info), 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|SLAB_ACCOUNT, - offsetof(struct jfs_inode_info, i_inline), - sizeof_field(struct jfs_inode_info, i_inline), + offsetof(struct jfs_inode_info, i_inline), IDATASIZE, init_once); if (jfs_inode_cachep == NULL) return -ENOMEM; |