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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>:
#include <fstream>
int
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);
output.close();
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
*** Bug 814296 has been marked as a duplicate of this bug. ***
Comment 3RHEL Program Management
2012-04-19 14:50:03 UTC
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.
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
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.
http://rhn.redhat.com/errata/RHSA-2012-0862.html
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>: #include <fstream> int 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); output.close(); 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