[Bug libc/4714] New: bus error when trying to access page created by mremap()

["tambewilliam at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

In the code below, I mmap() a single page of 4096 and simply mremap() the same
page to 2*4096 which is 8192.

Then when I try to write anywhere after 4096 bytes, in the newly expanded area.
I get Bus error.

Can somebody please help me?


#define _GNU_SOURCE
#include <sys/mman.h>
#include <unistd.h>

#include <stdio.h>

main() {
        void *ptr;
        if ((ptr=mmap(0, 4096, PROT_READ|PROT_WRITE,
                MAP_ANONYMOUS|MAP_SHARED|MAP_GROWSDOWN, 0, 0)) == -1) {
                printf("failed to mmap\n");
                return;
        }

        if ((ptr=mremap(ptr, 4096, 8192, MREMAP_MAYMOVE)) == -1) {
                printf("failed to mremap\n");
                return;
        }
        
        //why does this failed. I am well in the interval [4096, 8192]
        *(unsigned int *)(ptr + 4096 + 8)= 10;
}

-- 
           Summary: bus error when trying to access page created by mremap()
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: critical
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: tambewilliam at gmail dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=4714

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