4.17-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook keescook@chromium.org
commit 961b33c244e5ba1543ae26270a1ba29f29c2db83 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/jfs/jfs_dinode.h | 7 +++++++ fs/jfs/jfs_incore.h | 1 + fs/jfs/super.c | 3 +-- 3 files changed, 9 insertions(+), 2 deletions(-)
--- 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]; --- 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 --- 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;