From patchwork Fri Dec 23 02:56:42 2022
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From: Qu Wenruo <wqu@suse.com>
To: linux-btrfs@vger.kernel.org, fstests@vger.kernel.org
Subject: [PATCH] btrfs/154: migrate to python3
Date: Fri, 23 Dec 2022 10:56:42 +0800
Message-Id: <20221223025642.33496-1-wqu@suse.com>
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Test case btrfs/154 is still using python2 script, which is already EOL.
Some rolling distros like Archlinux is no longer providing python2
package anymore.

This means btrfs/154 will be harder and harder to run.

To fix the problem, migreate the python script to python3, this involves
the following changes:

- Change common/config to use python3
- Strong type conversion between string and bytes
  This means, anything involved in the forged bytes has to be bytes.

  And there is no safe way to convert forged bytes into string, unlike
  python2.
  I guess that's why the author went python2 in the first place.

  Thankfully os.rename() still accepts forged bytes.

- Use bytes specific checks for invalid chars.

The updated script can still cause the needed conflicts, can be verified
through "btrfs ins dump-tree" command.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Neal Gompa <neal@gompa.dev>
---
 common/config                   |  2 +-
 src/btrfs_crc32c_forged_name.py | 22 ++++++++++++++++------
 tests/btrfs/154                 |  4 ++--
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/common/config b/common/config
index b2802e5e..e2aba5a9 100644
--- a/common/config
+++ b/common/config
@@ -212,7 +212,7 @@ export NFS4_SETFACL_PROG="$(type -P nfs4_setfacl)"
 export NFS4_GETFACL_PROG="$(type -P nfs4_getfacl)"
 export UBIUPDATEVOL_PROG="$(type -P ubiupdatevol)"
 export THIN_CHECK_PROG="$(type -P thin_check)"
-export PYTHON2_PROG="$(type -P python2)"
+export PYTHON3_PROG="$(type -P python3)"
 export SQLITE3_PROG="$(type -P sqlite3)"
 export TIMEOUT_PROG="$(type -P timeout)"
 export SETCAP_PROG="$(type -P setcap)"
diff --git a/src/btrfs_crc32c_forged_name.py b/src/btrfs_crc32c_forged_name.py
index 6c08fcb7..d29bbb70 100755
--- a/src/btrfs_crc32c_forged_name.py
+++ b/src/btrfs_crc32c_forged_name.py
@@ -59,9 +59,10 @@ class CRC32(object):
     # deduce the 4 bytes we need to insert
     for c in struct.pack('<L',fwd_crc)[::-1]:
       bkd_crc = ((bkd_crc << 8) & 0xffffffff) ^ self.reverse[bkd_crc >> 24]
-      bkd_crc ^= ord(c)
+      bkd_crc ^= c
 
-    res = s[:pos] + struct.pack('<L', bkd_crc) + s[pos:]
+    res = bytes(s[:pos], 'ascii') + struct.pack('<L', bkd_crc) + \
+          bytes(s[pos:], 'ascii')
     return res
 
   def parse_args(self):
@@ -72,6 +73,12 @@ class CRC32(object):
                         help="number of forged names to create")
     return parser.parse_args()
 
+def has_invalid_chars(result: bytes):
+    for i in result:
+        if i == 0 or i == int.from_bytes(b'/', byteorder="little"):
+            return True
+    return False
+
 if __name__=='__main__':
 
   crc = CRC32()
@@ -80,12 +87,15 @@ if __name__=='__main__':
   args = crc.parse_args()
   dirpath=args.dir
   while count < args.count :
-    origname = os.urandom (89).encode ("hex")[:-1].strip ("\x00")
+    origname = os.urandom (89).hex()[:-1].strip ("\x00")
     forgename = crc.forge(wanted_crc, origname, 4)
-    if ("/" not in forgename) and ("\x00" not in forgename):
+    if not has_invalid_chars(forgename):
       srcpath=dirpath + '/' + str(count)
-      dstpath=dirpath + '/' + forgename
-      file (srcpath, 'a').close()
+      # We have to convert all strings to bytes to concatenate the forged
+      # name (bytes).
+      # Thankfully os.rename() can accept bytes directly.
+      dstpath=bytes(dirpath, "ascii") + bytes('/', "ascii") + forgename
+      open(srcpath, mode="a").close()
       os.rename(srcpath, dstpath)
       os.system('btrfs fi sync %s' % (dirpath))
       count+=1;
diff --git a/tests/btrfs/154 b/tests/btrfs/154
index 240c504c..6be2d5f6 100755
--- a/tests/btrfs/154
+++ b/tests/btrfs/154
@@ -21,7 +21,7 @@ _begin_fstest auto quick
 
 _supported_fs btrfs
 _require_scratch
-_require_command $PYTHON2_PROG python2
+_require_command $PYTHON3_PROG python3
 
 # Currently in btrfs the node/leaf size can not be smaller than the page
 # size (but it can be greater than the page size). So use the largest
@@ -42,7 +42,7 @@ _scratch_mount
 #    ...
 #
 
-$PYTHON2_PROG $here/src/btrfs_crc32c_forged_name.py -d $SCRATCH_MNT -c 310
+$PYTHON3_PROG $here/src/btrfs_crc32c_forged_name.py -d $SCRATCH_MNT -c 310
 echo "Silence is golden"
 
 # success, all done