From e7e8937625f5a62f8f15a0dcf98546113446675e Mon Sep 17 00:00:00 2001 From: M A Young Date: Wed, 4 Jul 2012 15:46:14 +0100 Subject: pygrub: cope better with big files in the guest. Only read the first megabyte of a configuration file (grub etc.) and read the kernel and ramdisk files from the guest in one megabyte pieces so pygrub doesn't use a lot of memory if the files are large. With --not-really option check that the chosen kernel and ramdisk files exist. If there are problems writing the copy of the kernel or ramdisk, delete the copied files and exit in case they have filled the filesystem. Signed-off-by: Michael Young Acked-by: Matt Wilson Acked-by: Ian Campbell Acked-by: Ian Jackson Committed-by: Ian Campbell --- tools/pygrub/src/pygrub | 61 +++++++++++++++++++++++++++++++++++-------------- 1 file changed, 44 insertions(+), 17 deletions(-) (limited to 'tools/pygrub') diff --git a/tools/pygrub/src/pygrub b/tools/pygrub/src/pygrub index e14df3f45c..6dd44ace6a 100644 --- a/tools/pygrub/src/pygrub +++ b/tools/pygrub/src/pygrub @@ -28,6 +28,7 @@ import grub.LiloConf import grub.ExtLinuxConf PYGRUB_VER = 0.6 +FS_READ_MAX = 1024 * 1024 def enable_cursor(ison): if ison: @@ -448,7 +449,8 @@ class Grub: if self.__dict__.get('cf', None) is None: raise RuntimeError, "couldn't find bootloader config file in the image provided." f = fs.open_file(self.cf.filename) - buf = f.read() + # limit read size to avoid pathological cases + buf = f.read(FS_READ_MAX) del f self.cf.parse(buf) @@ -697,6 +699,37 @@ if __name__ == "__main__": def usage(): print >> sys.stderr, "Usage: %s [-q|--quiet] [-i|--interactive] [-n|--not-really] [--output=] [--kernel=] [--ramdisk=] [--args=] [--entry=] [--output-directory=] [--output-format=sxp|simple|simple0] " %(sys.argv[0],) + def copy_from_image(fs, file_to_read, file_type, output_directory, + not_really): + if not_really: + if fs.file_exists(file_to_read): + return "<%s:%s>" % (file_type, file_to_read) + else: + sys.exit("The requested %s file does not exist" % file_type) + try: + datafile = fs.open_file(file_to_read) + except Exception, e: + print >>sys.stderr, e + sys.exit("Error opening %s in guest" % file_to_read) + (tfd, ret) = tempfile.mkstemp(prefix="boot_"+file_type+".", + dir=output_directory) + dataoff = 0 + while True: + data = datafile.read(FS_READ_MAX, dataoff) + if len(data) == 0: + os.close(tfd) + del datafile + return ret + try: + os.write(tfd, data) + except Exception, e: + print >>sys.stderr, e + os.close(tfd) + os.unlink(ret) + del datafile + sys.exit("Error writing temporary copy of "+file_type) + dataoff += len(data) + try: opts, args = getopt.gnu_getopt(sys.argv[1:], 'qinh::', ["quiet", "interactive", "not-really", "help", @@ -821,24 +854,18 @@ if __name__ == "__main__": if not fs: raise RuntimeError, "Unable to find partition containing kernel" - if not_really: - bootcfg["kernel"] = "" % chosencfg["kernel"] - else: - data = fs.open_file(chosencfg["kernel"]).read() - (tfd, bootcfg["kernel"]) = tempfile.mkstemp(prefix="boot_kernel.", - dir=output_directory) - os.write(tfd, data) - os.close(tfd) + bootcfg["kernel"] = copy_from_image(fs, chosencfg["kernel"], "kernel", + output_directory, not_really) if chosencfg["ramdisk"]: - if not_really: - bootcfg["ramdisk"] = "" % chosencfg["ramdisk"] - else: - data = fs.open_file(chosencfg["ramdisk"],).read() - (tfd, bootcfg["ramdisk"]) = tempfile.mkstemp( - prefix="boot_ramdisk.", dir=output_directory) - os.write(tfd, data) - os.close(tfd) + try: + bootcfg["ramdisk"] = copy_from_image(fs, chosencfg["ramdisk"], + "ramdisk", output_directory, + not_really) + except: + if not not_really: + os.unlink(bootcfg["kernel"]) + raise else: initrd = None -- cgit v1.2.3