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Mike Frysinger 6b899c4e9a binfmt_misc: add comments & debug logs 
When trying to develop a custom format handler, the errors returned all
effectively get bucketed as EINVAL with no kernel messages.  The other
errors (ENOMEM/EFAULT) are internal/obvious and basic.  Thus any time a
bad handler is rejected, the developer has to walk the dense code and
try to guess where it went wrong.  Needing to dive into kernel code is
itself a fairly high barrier for a lot of people.

To improve this situation, let's deploy extensive pr_debug markers at
logical parse points, and add comments to the dense parsing logic.  It
let's you see exactly where the parsing aborts, the string the kernel
received (useful when dealing with shell code), how it translated the
buffers to binary data, and how it will apply the mask at runtime.

Some example output:
  $ echo ':qemu-foo:M::\x7fELF\xAD\xAD\x01\x00:\xff\xff\xff\xff\xff\x00\xff\x00:/usr/bin/qemu-foo:POC' > register
  $ dmesg
  binfmt_misc: register: received 92 bytes
  binfmt_misc: register: delim: 0x3a {:}
  binfmt_misc: register: name: {qemu-foo}
  binfmt_misc: register: type: M (magic)
  binfmt_misc: register: offset: 0x0
  binfmt_misc: register: magic[raw]: 5c 78 37 66 45 4c 46 5c 78 41 44 5c 78 41 44 5c  \x7fELF\xAD\xAD\
  binfmt_misc: register: magic[raw]: 78 30 31 5c 78 30 30 00                          x01\x00.
  binfmt_misc: register:  mask[raw]: 5c 78 66 66 5c 78 66 66 5c 78 66 66 5c 78 66 66  \xff\xff\xff\xff
  binfmt_misc: register:  mask[raw]: 5c 78 66 66 5c 78 30 30 5c 78 66 66 5c 78 30 30  \xff\x00\xff\x00
  binfmt_misc: register:  mask[raw]: 00                                               .
  binfmt_misc: register: magic/mask length: 8
  binfmt_misc: register: magic[decoded]: 7f 45 4c 46 ad ad 01 00                          .ELF....
  binfmt_misc: register:  mask[decoded]: ff ff ff ff ff 00 ff 00                          ........
  binfmt_misc: register:  magic[masked]: 7f 45 4c 46 ad 00 01 00                          .ELF....
  binfmt_misc: register: interpreter: {/usr/bin/qemu-foo}
  binfmt_misc: register: flag: P (preserve argv0)
  binfmt_misc: register: flag: O (open binary)
  binfmt_misc: register: flag: C (preserve creds)

The [raw] lines show us exactly what was received from userspace.  The
lines after that show us how the kernel has decoded things.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2014-12-10 17:41:12 -08:00
..
9p 9p: switch to %p[dD] 2014-10-09 02:39:04 -04:00
adfs adfs: add __printf verification, fix format/argument mismatches 2014-08-08 15:57:24 -07:00
affs fs/affs: remove redundant sys_tz declarations 2014-10-14 02:18:22 +02:00
afs Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-13 16:23:15 +02:00
autofs4 autofs4: d_manage() should return -EISDIR when appropriate in rcu-walk mode. 2014-10-14 02:18:16 +02:00
befs fs/befs/btree.c: remove typedef befs_btree_node 2014-10-14 02:18:20 +02:00
bfs fs/bfs: use bfs prefix for dump_imap 2014-08-08 15:57:24 -07:00
btrfs btrfs: zero out left over bytes after processing compression streams 2014-11-30 09:33:51 -08:00
cachefiles FS-Cache fixes 2014-10-14 08:40:15 +02:00
ceph ceph: fix flush tid comparision 2014-11-13 22:19:05 +03:00
cifs fs/cifs/smb2file.c: replace count*size kzalloc by kcalloc 2014-12-10 17:41:02 -08:00
coda fs/coda: use linux/uaccess.h 2014-08-08 15:57:20 -07:00
configfs fs/configfs: use pr_fmt 2014-06-04 16:53:53 -07:00
cramfs fs/cramfs/inode.c: use linux/uaccess.h 2014-08-08 15:57:25 -07:00
debugfs fs: debugfs: remove trailing whitespace 2014-07-09 16:58:21 -07:00
devpts fs/devpts/inode.c: convert printk to pr_foo() 2014-06-06 16:08:14 -07:00
dlm dlm: fix missing endian conversion of rcom_status flags 2014-10-14 15:11:48 -05:00
ecryptfs fs: limit filesystem stacking depth 2014-10-24 00:14:39 +02:00
efivarfs fs/efivarfs/super.c: use static const for dentry_operations 2014-06-04 16:54:14 -07:00
efs fs/efs/namei.c: return is not a function 2014-08-08 15:57:18 -07:00
exofs Boaz Harrosh - Fix broken email address 2014-10-19 20:22:32 +03:00
exportfs fs/exportfs/expfs.c: kernel-doc warning fixes 2014-06-04 16:54:14 -07:00
ext2 percpu_counter: add @gfp to percpu_counter_init() 2014-09-08 09:51:29 +09:00
ext3 ext3: Don't check quota format when there are no quota files 2014-10-22 09:02:48 +02:00
ext4 ext4: make ext4_ext_convert_to_initialized() return proper number of blocks 2014-10-30 10:53:17 -04:00
f2fs f2fs: support volatile operations for transient data 2014-10-07 11:54:41 -07:00
fat fat: fix oops on corrupted vfat fs 2014-12-03 09:36:03 -08:00
freevxfs Major changes for 3.14 include support for the newly added ZERO_RANGE 2014-04-04 15:39:39 -07:00
fscache fs/fscache/object-list.c: use __seq_open_private() 2014-10-13 17:52:21 +01:00
fuse vfs: Make d_invalidate return void 2014-10-09 02:38:57 -04:00
gfs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-10-13 11:28:42 +02:00
hfs fs/hfs/hfs_fs.h: remove redundant sys_tz declaration 2014-10-14 02:18:20 +02:00
hfsplus Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-06-12 10:30:18 -07:00
hostfs hostfs: support rename flags 2014-08-07 14:40:09 -04:00
hpfs fs/hpfs/dnode.c: fix suspect code indent 2014-08-08 15:57:22 -07:00
hppfs
…
hugetlbfs fs/hugetlbfs/inode.c: remove null test before kfree 2014-06-04 16:54:11 -07:00
isofs isofs: avoid unused function warning 2014-11-19 13:09:37 -05:00
jbd fs, jbd: use a more generic hash function 2014-10-22 10:02:04 +02:00
jbd2 jbd2: fix regression where we fail to initialize checksum seed when loading 2014-12-01 21:57:06 -05:00
jffs2 [jffs2] kill wbuf_queued/wbuf_dwork_lock 2014-10-09 02:39:01 -04:00
jfs Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-13 16:23:15 +02:00
kernfs vfs: Remove unnecessary calls of check_submounts_and_drop 2014-10-09 02:38:56 -04:00
lockd File locking related changes for v3.18 (pile #1) 2014-10-11 13:21:34 -04:00
logfs fs/logfs/readwrite.c: kernel-doc warning fixes 2014-08-06 18:01:12 -07:00
minix minix zmap block counts calculation fix 2014-08-08 15:57:20 -07:00
ncpfs fs/ncpfs/dir.c: remove redundant sys_tz declaration 2014-10-14 02:18:16 +02:00
nfs NFS: Don't try to reclaim delegation open state if recovery failed 2014-11-12 17:19:04 -05:00
nfs_common lockd: move lockd's grace period handling into its own module 2014-09-17 16:33:11 -04:00
nfsd nfsd: Fix slot wake up race in the nfsv4.1 callback code 2014-11-19 15:45:44 -05:00
nilfs2 nilfs2: improve the performance of fdatasync() 2014-10-14 02:18:20 +02:00
nls
…
notify Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-09 21:21:34 -08:00
ntfs NTFS: Bump version to 2.1.31. 2014-10-16 12:53:35 +01:00
ocfs2 ocfs2: remove unneeded NULL check 2014-12-10 17:41:04 -08:00
omfs FS/OMFS: block number sanity check during fill_super operation 2014-10-14 02:18:22 +02:00
openpromfs fs: push sync_filesystem() down to the file system's remount_fs() 2014-03-13 10:14:33 -04:00
overlayfs ovl: ovl_dir_fsync() cleanup 2014-11-20 16:40:02 +01:00
proc proc: task_state: ptrace_parent() doesn't need pid_alive() check 2014-12-10 17:41:09 -08:00
pstore pstore: Fix duplicate {console,ftrace}-efi entries 2014-10-15 13:51:33 -07:00
qnx4 fs: push sync_filesystem() down to the file system's remount_fs() 2014-03-13 10:14:33 -04:00
qnx6 fs/qnx6: update debugging to current functions 2014-08-08 15:57:26 -07:00
quota quota: Properly return errors from dquot_writeback_dquots() 2014-10-22 09:08:03 +02:00
ramfs fs/ramfs/file-nommu.c: replace count*size kzalloc by kcalloc 2014-08-08 15:57:18 -07:00
reiserfs fs/reiserfs/journal.c: fix sparse context imbalance warning 2014-10-14 02:18:20 +02:00
romfs fs/romfs/super.c: add blank line after declarations 2014-08-08 15:57:25 -07:00
squashfs fs/squashfs/super.c: logging cleanup 2014-08-06 18:01:13 -07:00
sysfs kernfs: move the last knowledge of sysfs out from kernfs 2014-06-03 08:11:18 -07:00
sysv write_iter variants of {__,}generic_file_aio_write() 2014-05-06 17:38:00 -04:00
ubifs UBIFS: Fix trivial typo in power_cut_emulated() 2014-09-30 09:29:44 +03:00
udf udf: Fix loading of special inodes 2014-10-09 13:06:14 +02:00
ufs fs/ufs/balloc.c: remove unused variable 2014-10-14 02:18:20 +02:00
xfs xfs: track bulkstat progress by agino 2014-11-07 08:33:52 +11:00
Kconfig overlay filesystem 2014-10-24 00:14:38 +02:00
Kconfig.binfmt
…
Makefile ovl: rename filesystem type to "overlay" 2014-11-20 16:39:59 +01:00
aio.c Merge git://git.kvack.org/~bcrl/aio-fixes 2014-11-25 18:55:44 -08:00
anon_inodes.c vfs: Allocate anon_inode_inode in anon_inode_init() 2014-03-27 09:52:54 -07:00
attr.c fs,userns: Change inode_capable to capable_wrt_inode_uidgid 2014-06-10 13:57:22 -07:00
bad_inode.c bad_inode: add ->rename2() 2014-08-07 14:40:09 -04:00
binfmt_aout.c handle suicide on late failure exits in execve() in search_binary_handler() 2014-10-09 02:39:00 -04:00
binfmt_elf.c handle suicide on late failure exits in execve() in search_binary_handler() 2014-10-09 02:39:00 -04:00
binfmt_elf_fdpic.c handle suicide on late failure exits in execve() in search_binary_handler() 2014-10-09 02:39:00 -04:00
binfmt_em86.c
…
binfmt_flat.c fs/binfmt_flat.c: make old_reloc() static 2014-06-04 16:54:21 -07:00
binfmt_misc.c binfmt_misc: add comments & debug logs 2014-12-10 17:41:12 -08:00
binfmt_script.c
…
binfmt_som.c
…
block_dev.c Return short read or 0 at end of a raw device, not EIO 2014-10-31 06:33:26 -04:00
buffer.c fs: clarify rate limit suppressed buffer I/O errors 2014-10-21 13:55:11 -06:00
char_dev.c fs/char_dev.c: remove pointless assignment from __register_chrdev_region() 2014-12-10 17:41:04 -08:00
compat.c vfs: move getname() from callers to do_mount() 2014-10-09 02:39:16 -04:00
compat_binfmt_elf.c binfmt_elf: add ELF_HWCAP2 to compat auxv entries 2014-03-04 08:05:21 +00:00
compat_ioctl.c Bluetooth: Move HCI socket definitions into its own header file 2014-07-11 13:53:04 +03:00
coredump.c coredump: add %i/%I in core_pattern to report the tid of the crashed thread 2014-10-14 02:18:21 +02:00
dcache.c vfs: fix reference leak in d_prune_aliases() 2014-11-19 13:07:20 -05:00
dcookies.c
…
direct-io.c fuse: honour max_read and max_write in direct_io mode 2014-09-26 21:16:51 -04:00
drop_caches.c fs: convert use of typedef ctl_table to struct ctl_table 2014-06-06 16:08:16 -07:00
eventfd.c
…
eventpoll.c eventpoll: fix uninitialized variable in epoll_ctl 2014-09-10 15:42:12 -07:00
exec.c fs: Do not include mpx.h in exec.c 2014-11-18 02:01:40 +01:00
fcntl.c security: make security_file_set_fowner, f_setown and __f_setown void return 2014-09-09 16:01:36 -04:00
fhandle.c
…
file.c fs/file.c: replace get_unused_fd() with get_unused_fd_flags(0) 2014-12-10 17:41:10 -08:00
file_table.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-10-13 11:28:42 +02:00
filesystems.c sys_sysfs: Add CONFIG_SYSFS_SYSCALL 2014-04-03 16:21:05 -07:00
fs-writeback.c sched: Remove proliferation of wait_on_bit() action functions 2014-07-16 15:10:39 +02:00
fs_pin.c make fs/{namespace,super}.c forget about acct.h 2014-08-07 14:40:09 -04:00
fs_struct.c
…
inode.c mm: allow drivers to prevent new writable mappings 2014-08-08 15:57:31 -07:00
internal.h vfs: export __inode_permission() to modules 2014-10-24 00:14:35 +02:00
ioctl.c
…
libfs.c locks: plumb a "priv" pointer into the setlease routines 2014-10-07 14:06:12 -04:00
locks.c locks: flock_make_lock should return a struct file_lock (or PTR_ERR) 2014-10-07 14:06:13 -04:00
mbcache.c fs/mbcache: replace __builtin_log2() with ilog2() 2014-06-25 22:08:29 -04:00
mount.h vfs: Add a function to lazily unmount all mounts from any dentry. 2014-10-09 02:38:55 -04:00
mpage.c vfs: guard end of device for mpage interface 2014-10-09 22:25:53 -04:00
namei.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-11-02 10:28:43 -08:00
namespace.c vfs: introduce clone_private_mount() 2014-10-24 00:14:36 +02:00
no-block.c
…
open.c vfs: add i_op->dentry_open() 2014-10-24 00:14:35 +02:00
pipe.c new helper: copy_page_from_iter() 2014-05-06 17:39:42 -04:00
pnode.c get rid of propagate_umount() mistakenly treating slaves as busy. 2014-08-30 18:31:41 -04:00
pnode.h smarter propagate_mnt() 2014-04-01 23:19:08 -04:00
posix_acl.c posix_acl: handle NULL ACL in posix_acl_equiv_mode 2014-05-06 13:58:42 -04:00
proc_namespace.c namespaces: Use task_lock and not rcu to protect nsproxy 2014-07-29 18:08:50 -07:00
read_write.c cachefiles_write_page(): switch to __kernel_write() 2014-10-09 02:39:05 -04:00
readdir.c fanotify: create FAN_ACCESS event for readdir 2014-06-04 16:53:52 -07:00
select.c
…
seq_file.c fs/seq_file: fallback to vmalloc allocation 2014-07-03 09:21:54 -07:00
signalfd.c
…
splice.c vfs: export do_splice_direct() to modules 2014-10-24 00:14:35 +02:00
stack.c fs: fix comment for 'CONFIG_LBADF' 2014-08-26 09:35:56 +02:00
stat.c
…
statfs.c
…
super.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-10-13 11:28:42 +02:00
sync.c Export sync_filesystem() for modular ->remount_fs() use 2014-09-05 08:16:21 -07:00
timerfd.c timerfd: Remove an always true check 2014-08-27 11:17:48 +02:00
utimes.c
…
xattr.c vfs: Deduplicate code shared by xattr system calls operating on paths 2014-10-12 17:09:10 -04:00