re: Kernel oops in read()

[Larry Sendlosky <larry scrugs lkg dec com>]

Resend - I forgot to include kernel version on XP1000, and original
mail had bogus mail addr for axp-list..... larry


On a DP264 running 2.4-test1 (RedHat 6.1, or 6.2, I forget) libc 2.1.3.
Program loops and strace shows

read(3, 0, 1768849408)                  = -1 EFAULT (Bad address)
read(3, 0, 1768849408)                  = -1 EFAULT (Bad address)
....

On a XP1000 2.2.15 with RedHat 6.1, libc 2.1.2
The program segfaults.. 

> ./test
fd = 3
Segmentation fault
>                      




> This is kernel 2.2.15 or 2.2.16pre7 (same on both).  The following
> test program, run as *ANY* user on the system (not just root), causes
> a segfault (expected) and a kernel oops every time it is run.  (Note:
> this malloc is supposed to fail.  If it gets that much RAM on your
> system, buy a slower box <g>)
> 
> #include <stdio.h>
> #include <unistd.h>
> #include <sys/types.h>
> #include <fcntl.h>
> 
> void main(void) {
>   int fd;
>   char *buf;
>   
>   fd = open("/bin/bash", O_RDONLY);
>   lseek(fd, 98, SEEK_SET);
>   buf = malloc(1768849408);
>   printf("fd = %d\n", fd);
>   while (1) {
>     read(fd, buf, 1768849408);
>   }
> }
> 
> Strace gives:
> 
> write(1, "fd = 3\n", 7fd = 3
> )                 = 7
> read(3,  <unfinished ...>
> +++ killed by SIGSEGV +++
> 
> The platform is DEC Alpha, 21164a CPU, 256M RAM, Debian.
> 
> The oops is:
> 
> Unable to handle kernel paging request at virtual address 0000000000000000
> test(3515): Oops 1
> pc = [<fffffc0000468a74>]  ra = [<fffffc0000335140>]  ps = 0000
> v0 = 0000000000001f9e  t0 = 0150000000000000  t1 = 0000000000000150
> t2 = 0000000000000000  t3 = 0000000000001f90  t4 = 0000000000000114
> t5 = 0000000000000000  t6 = fffffc000fb3c062  t7 = fffffc0008710000
> s0 = 0000000000001f9e  s1 = fffffc0000793b28  s2 = fffffc00000309e0
> s3 = 0000000000000000  s4 = 0000000000000000  s5 = fffffc000029dd40
> s6 = 0000000000000000  a0 = fffffc0008713ec8  a1 = fffffc000fb3c062
> a2 = 0000000000001f9e  a3 = fffffc0000335400  a4 = ffffffffffffffff
> a5 = 0000000000000007  t8 = 0000000000001f9e  t9 = 00000000696e8000
> t10= 3000000000000000  t11= 000000000000000a  pv = fffffc00004689e0
> at = fffffc000033542c  gp = fffffc00004e3c78  sp = fffffc0008713e38
> Code:
>  2fe00000  ldq_u zero,0(v0)
>  2c470008  ldq_u t1,8(t6)
>  40811524  subq t3,8,t3
>  486706c3  extql t2,t6,t2
>  48470f41  ALU t1,t6,t0
>  44610401  or t2,t0,t0
> *b4260000  stq t0,0(t5)
>  40e11407  addq t6,8,t6
> Trace: 3354d8 335400 34238c 310e4c 
> 
> -

______________________________________________________________________
 Larry Sendlosky			 	            ATS
 larry@scrugs.lkg.dec.com (978) 506-6640                    Compaq
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