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kernel: prohibit changing cache attributes (SG_CACHED|SG_DEVICE) in segattach(), set SG_RONLY in data2txt()

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the user should not be able to change the cache
attributes for a segment in segattach() as this
can cause the same memory to be mapped with
conflicting attributes in the cache.

SG_TEXT should always be mapped with SG_RONLY
attribute. so fix data2txt() to follow the rules.
This commit is contained in:
cinap_lenrek 2019-08-27 06:16:20 +02:00
parent d25ca13ed8
commit d9fec3c70a
2 changed files with 10 additions and 7 deletions
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15
sys/src/9/port/segment.c
View file

@ -177,8 +177,8 @@ dupseg(Segment **seg, int segno, int share)
case SG_DATA: /* Copy on write plus demand load info */
if(segno == TSEG){
n = data2txt(s);
poperror();
qunlock(s);
poperror();
return n;
}
@ -200,14 +200,14 @@ dupseg(Segment **seg, int segno, int share)
n->flushme = s->flushme;
if(s->ref > 1)
procflushseg(s);
poperror();
qunlock(s);
poperror();
return n;
sameseg:
incref(s);
poperror();
qunlock(s);
poperror();
return s;
}
@ -680,8 +680,11 @@ segattach(int attr, char *name, uintptr va, uintptr len)
if(len > ps->size)
error(Enovmem);
attr &= ~SG_TYPE; /* Turn off what is not allowed */
attr |= ps->attr; /* Copy in defaults */
/* Turn off what is not allowed */
attr &= ~(SG_TYPE | SG_CACHED | SG_DEVICE);
/* Copy in defaults */
attr |= ps->attr;
s = newseg(attr, va, len/BY2PG);
s->pseg = ps;
@ -788,7 +791,7 @@ data2txt(Segment *s)
{
Segment *ps;
ps = newseg(SG_TEXT, s->base, s->size);
ps = newseg(SG_TEXT | SG_RONLY, s->base, s->size);
ps->image = s->image;
incref(ps->image);
ps->fstart = s->fstart;

2
sys/src/9/port/sysproc.c
View file

@ -512,7 +512,7 @@ sysexec(va_list list)
/* Text. Shared. Attaches to cache image if possible */
/* attachimage returns a locked cache image */
img = attachimage(SG_TEXT|SG_RONLY, tc, UTZERO, (t-UTZERO)>>PGSHIFT);
img = attachimage(SG_TEXT | SG_RONLY, tc, UTZERO, (t-UTZERO)>>PGSHIFT);
ts = img->s;
up->seg[TSEG] = ts;
ts->flushme = 1;