0001303: mmap: unsigned shift operation => overflow error

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Category

Severity

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Date Submitted

Last Update

0001303

[uClibc] Architecture Specific

major

always

04-05-07 01:47

09-26-08 01:26

Reporter

anlo

View Status

public

Assigned To

uClibc

Priority

normal

Resolution

fixed

Status

closed

Product Version

Summary

0001303: mmap: unsigned shift operation => overflow error

Description

Product version: 0.9.29 (2007-04-02)

When trying to map /dev/mem with offset 0xFFFFF000 on the ARM platform, mmap returns -EOVERFLOW. After some investigation, I have found the cause in uClibc/libc/sysdeps/linux/arm/mmap.c:

Since off_t is defined as a long int and the sign bit is set in the address, the shift operation at line 45 (see below) shifts in ones instead of zeroes from the left. This results the offset sent to the kernel function becomes 0xFFFFFFFF instead of 0x000FFFFF with MMAP2_PAGE_SHIFT set to 12.

(off_t) (offset >> MMAP2_PAGE_SHIFT)

Proposed change, since the kernel function (do_mmap) expects offset as unsigned long:

((unsigned long) offset >> MMAP2_PAGE_SHIFT)

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Notes
(0002350) khem 05-09-07 13:25	Yes this should fix the problem. I verified it. However the same fix needs to be applied to ./libc/sysdeps/linux/common/mmap64.c as well

(0002358) khem 05-14-07 17:40	A patch which fixes this problem has been installed on trunk. Please verify with the latest trunk. here is the patch as applied. http://uclibc.org/lists/uclibc-cvs/2007-May/011360.html [^]

Issue History
Date Modified	Username	Field	Change
04-05-07 01:47	anlo	New Issue
04-05-07 01:47	anlo	Status	new => assigned
04-05-07 01:47	anlo	Assigned To	=> uClibc
04-05-07 01:50	anlo	Issue Monitored: anlo
05-09-07 13:25	khem	Note Added: 0002350
05-14-07 17:40	khem	Note Added: 0002358
09-26-08 01:26	bernhardf	Status	assigned => closed
09-26-08 01:26	bernhardf	Resolution	open => fixed
09-26-08 01:26	bernhardf	Fixed in Version	=> 0.9.30