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kbmap: fix sprint() buffer overflow (thanks silasm)

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A buffer can be overflowed in the init function of kbmap.c by using a filename of more than 112 characters.

sample output:
% cd /sys/lib/kbmap
% touch aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
% kbmap
kbmap 1974: suicide: sys: trap: fault write addr=0xa6a96510 pc=0x000011df
offending code is most likely the call to sprint in the init function of /sys/src/cmd/kbmap.c,
which in this case writes /sys/lib/kbmap/$file to a 128-bit buffer.
I'm willing to submit a patch for this myself along with a few minor improvements/fixes to kbmap
if I can figure out the nuances of doing so.

--silasm
This commit is contained in:
cinap_lenrek 2014-12-11 18:32:50 +01:00
parent ffa761beae
commit 86e63c36ed
1 changed files with 2 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

5
sys/src/cmd/kbmap.c
View file

@ -64,7 +64,6 @@ init(void)
{
int i, fd, nr;
Dir *pd;
char buf[128];
if((fd = open(dir, OREAD)) < 0)
return;
@ -72,8 +71,8 @@ init(void)
nmap = nr = dirreadall(fd, &pd);
map = emalloc(nr * sizeof(KbMap));
for(i=0; i<nr; i++){
sprint(buf, "%s/%s", dir, pd[i].name);
map[i].file = estrdup(buf);
map[i].file = emalloc(strlen(dir) + strlen(pd[i].name) + 2);
sprint(map[i].file, "%s/%s", dir, pd[i].name);
map[i].name = estrdup(pd[i].name);
map[i].current = 0;
}