Bug 814302 - large writes to ext4 may return incorrect value
large writes to ext4 may return incorrect value
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel (Show other bugs)
x86_64 Linux
unspecified Severity unspecified
: rc
: ---
Assigned To: Eric Sandeen
Eryu Guan
: 814296 (view as bug list)
Depends On:
  Show dependency treegraph
Reported: 2012-04-19 10:39 EDT by Eric Sandeen
Modified: 2012-06-20 04:48 EDT (History)
2 users (show)

See Also:
Fixed In Version: kernel-2.6.32-266.el6
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2012-06-20 04:48:04 EDT
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Eric Sandeen 2012-04-19 10:39:02 EDT
Description of problem:

ext4_file_write returns an int, rather than a ssize_t, so large values may overflow, and return incorrect values to userspace.

This is fixed with a simple one-liner to change the return value of ext4_file_write() to a ssize_t.

Version-Release number of selected component (if applicable):

Any recent RHEL6 kernel

How reproducible:

every time

Steps to Reproduce:

From the upstream mailing list as reported by Jouni Siren <jouni.siren@iki.fi>:

#include <fstream>

main(int argc, char** argv)
  std::streamsize data_size = (std::streamsize)1 << 31;
  char* data = new char[data_size];

  std::ofstream output("test.dat", std::ios_base::binary);
  output.write(data, 8);
  output.write(data, data_size);
  output.write(data, data_size);

  delete[] data;
  return 0;

Note the failing writev() with the large negative number:

open("test.dat", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
writev(3, [{"\0\0\0\0\0\0\0\0", 8}, {"", 2147483648}], 2) = -2147483640
writev(3, [{0xffffffff80c6d258, 2147483648}, {"", 2147483648}], 2) = -1 EFAULT (Bad address)
write(3, "\0\0\0\0\0\0\0\0", 8)         = 8
close(3)                                = 0
Comment 1 Eric Sandeen 2012-04-19 10:39:51 EDT
(Note, RHEL5 is not affected)
Comment 2 Eric Sandeen 2012-04-19 10:45:32 EDT
*** Bug 814296 has been marked as a duplicate of this bug. ***
Comment 3 RHEL Product and Program Management 2012-04-19 10:50:03 EDT
This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.
Comment 5 Aristeu Rozanski 2012-04-23 12:01:15 EDT
Patch(es) available on kernel-2.6.32-266.el6
Comment 8 Eryu Guan 2012-04-26 05:04:43 EDT
Seems this only affects writev(2) system call

Reproduced on kernel-2.6.32-250.el6

writev(2) returns negative value
writev(3, [{"", 2147483648}], 1)        = -2147483648

write(2) does a partial write
write(3, "", 2147483648)                = 2147479552

Verified on kernel-2.6.32-266.el6

writev(2) returns correct value
writev(3, [{"", 2147483648}], 1)        = 2147483648

write(2) also returns no error, but partial write
write(3, "", 2147483648)                = 2147479552
Comment 10 errata-xmlrpc 2012-06-20 04:48:04 EDT
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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