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kernel: fix stat bugs

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In a few places, we where using a fixed buffer of sizeof(Dir)+100
size for stat. This is not correct and fails if the name returned
in stat is long.

This results in being unable to seek to the end of file with a
long filename.

The kernel should do the same thing as dirfstat() from libc;
handling the conversion and buffer allocation and returning a
freeable Dir* pointer.

For this, a new dirchanstat() function was added.

The fstat syscall was not rewriting the name to the last path
element; fix it.

In addition, gracefully handle the mountfix case, reallocating
the buffer to accomidate the required stat length plus
size of the new name so dirsetname() does not fail.
This commit is contained in:
cinap_lenrek 2021-10-23 13:40:06 +00:00
parent e54b6c6cbd
commit db971a6189
6 changed files with 112 additions and 99 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

39
sys/src/9/port/chan.c
View file

@ -1720,3 +1720,42 @@ isdir(Chan *c)
return;
error(Enotdir);
}
enum
{
DIRSIZE = STATFIXLEN + 16 * 4 /* enough for encoded stat buf + some reasonable strings */
};
Dir*
dirchanstat(Chan *c)
{
Dir *d;
uchar *buf;
int n, nd, i;
nd = DIRSIZE;
for(i=0; i<2; i++){ /* should work by the second try */
d = smalloc(sizeof(Dir) + BIT16SZ + nd);
if(waserror()){
free(d);
nexterror();
}
buf = (uchar*)&d[1];
n = devtab[c->type]->stat(c, buf, BIT16SZ+nd);
if(n < BIT16SZ)
error(Eshortstat);
nd = GBIT16(buf); /* upper bound on size of Dir + strings */
if(nd <= n){
if(convM2D(buf, n, d, (char*)&d[1]) == 0)
error(Eshortstat);
poperror();
return d;
}
/* else sizeof(Dir)+BIT16SZ+nd is plenty */
free(d);
poperror();
}
error(Eshortstat);
return nil;
}

25
sys/src/9/port/devfs.c
View file

@ -553,18 +553,6 @@ parsename(char *name, char *disk, char **tree, char **dev)
validname(*dev, 0);
}
static vlong
getlen(Chan *c)
{
uchar buf[128]; /* old DIRLEN plus a little should be plenty */
Dir d;
long l;
l = devtab[c->type]->stat(c, buf, sizeof buf);
convM2D(buf, l, &d, nil);
return d.length;
}
/*
* Process a single line of configuration,
* often of the form "cmd newname idev0 idev1".
@ -602,8 +590,6 @@ mconfig(char* a, long n)
start = 0;
mp = nil;
cb = nil;
idev = nil;
ilen = nil;
keylen = 0;
if(waserror()){
@ -686,6 +672,8 @@ mconfig(char* a, long n)
*/
poperror();
rlock(&lck);
idev = smalloc(sizeof(Chan*) * Ndevs);
ilen = smalloc(sizeof(vlong) * Ndevs);
if(waserror()){
runlock(&lck);
Fail:
@ -699,11 +687,14 @@ Fail:
free(cb);
nexterror();
}
idev = smalloc(sizeof(Chan*) * Ndevs);
ilen = smalloc(sizeof(vlong) * Ndevs);
for(i = 1; i < cb->nf; i++){
Dir *dir;
idev[i-1] = namec(cb->f[i], Aopen, ORDWR, 0);
ilen[i-1] = getlen(idev[i-1]);
dir = dirchanstat(idev[i-1]);
ilen[i-1] = dir->length;
free(dir);
}
poperror();
runlock(&lck);

17
sys/src/9/port/devswap.c
View file

@ -383,10 +383,6 @@ needpages(void*)
static void
setswapchan(Chan *c)
{
uchar buf[sizeof(Dir)+100];
Dir d;
int n;
if(waserror()){
cclose(c);
nexterror();
@ -403,16 +399,17 @@ setswapchan(Chan *c)
* to be at most the size of the partition
*/
if(devtab[c->type]->dc != L'M'){
n = devtab[c->type]->stat(c, buf, sizeof buf);
if(n <= 0 || convM2D(buf, n, &d, nil) == 0)
error("stat failed in setswapchan");
if(d.length < (vlong)conf.nswppo*BY2PG)
Dir *d = dirchanstat(c);
if(d->length < (vlong)conf.nswppo*BY2PG){
free(d);
error("swap device too small");
if(d.length < (vlong)conf.nswap*BY2PG){
conf.nswap = d.length/BY2PG;
}
if(d->length < (vlong)conf.nswap*BY2PG){
conf.nswap = d->length/BY2PG;
swapalloc.top = &swapalloc.swmap[conf.nswap];
swapalloc.free = conf.nswap;
}
free(d);
}
c->flag &= ~CCACHE;
cclunk(c);

1
sys/src/9/port/portfns.h
View file

@ -79,6 +79,7 @@ void devshutdown(void);
int devstat(Chan*, uchar*, int, Dirtab*, int, Devgen*);
Walkqid* devwalk(Chan*, Chan*, char**, int, Dirtab*, int, Devgen*);
int devwstat(Chan*, uchar*, int);
Dir* dirchanstat(Chan *);
void drawactive(int);
void drawcmap(void);
void dumpaproc(Proc*);

17
sys/src/9/port/sdloop.c
View file

@ -47,21 +47,14 @@ SDifc sdloopifc;
static void
identify(Ctlr *c, SDunit *u)
{
int n;
uvlong s, osectors;
uchar buf[sizeof(Dir) + 100];
Dir dir;
Dir *dir;
if(waserror()){
iprint("sdloop: identify: %s\n", up->errstr);
nexterror();
}
osectors = c->sectors;
n = devtab[c->c->type]->stat(c->c, buf, sizeof buf);
if(convM2D(buf, n, &dir, nil) == 0)
error("internal error: stat error in seek");
s = dir.length / c->sectsize;
poperror();
dir = dirchanstat(c->c);
s = dir->length / c->sectsize;
free(dir);
memset(u->inquiry, 0, sizeof u->inquiry);
u->inquiry[2] = 2;

112
sys/src/9/port/sysfile.c
View file

@ -592,22 +592,26 @@ mountfix(Chan *c, uchar *op, long n, long maxn)
}
runlock(&mh->lock);
if(waserror())
goto Norewrite;
name = dirname(p, &nname);
/*
* Do the stat but fix the name. If it fails, leave old entry.
* BUG: If it fails because there isn't room for the entry,
* what can we do? Nothing, really. Might as well skip it.
*/
if(buf == nil){
nbuf = 4096;
buf = smalloc(nbuf);
}
if(waserror())
goto Norewrite;
l = devtab[nc->type]->stat(nc, buf, nbuf);
if(l < BIT16SZ)
error(Eshortstat);
rest = BIT16SZ + GBIT16(buf) + nname;
if(rest > nbuf){
free(buf);
nbuf = rest;
buf = smalloc(nbuf);
l = devtab[nc->type]->stat(nc, buf, nbuf);
}
l = dirsetname(name, nname, buf, l, nbuf);
if(l == BIT16SZ)
error("dirsetname");
if(l <= BIT16SZ)
error(Eshortstat);
poperror();
/*
@ -831,10 +835,8 @@ syspwrite(va_list list)
static vlong
sseek(int fd, vlong o, int type)
{
Dir *d;
Chan *c;
uchar buf[sizeof(Dir)+100];
Dir dir;
int n;
vlong off;
c = fdtochan(fd, -1, 1, 1);
@ -872,10 +874,9 @@ sseek(int fd, vlong o, int type)
case 2:
if(c->qid.type & QTDIR)
error(Eisdir);
n = devtab[c->type]->stat(c, buf, sizeof buf);
if(convM2D(buf, n, &dir, nil) == 0)
error("internal error: stat error in seek");
off = dir.length + o;
d = dirchanstat(c);
off = d->length + o;
free(d);
if(off < 0)
error(Enegoff);
c->offset = off;
@ -967,34 +968,36 @@ pathlast(Path *p)
uintptr
sysfstat(va_list list)
{
char *name;
uchar *s;
Chan *c;
int fd;
uint l;
uchar *s;
uint l, r;
fd = va_arg(list, int);
s = va_arg(list, uchar*);
l = va_arg(list, uint);
validaddr((uintptr)s, l, 1);
c = fdtochan(fd, -1, 0, 1);
if(waserror()) {
cclose(c);
nexterror();
}
l = devtab[c->type]->stat(c, s, l);
r = devtab[c->type]->stat(c, s, l);
if((name = pathlast(c->path)) != nil)
r = dirsetname(name, strlen(name), s, r, l);
poperror();
cclose(c);
return l;
return r;
}
uintptr
sysstat(va_list list)
{
char *name;
uchar *s;
Chan *c;
uint l, r;
uchar *s;
name = va_arg(list, char*);
s = va_arg(list, uchar*);
@ -1007,10 +1010,8 @@ sysstat(va_list list)
nexterror();
}
r = devtab[c->type]->stat(c, s, l);
name = pathlast(c->path);
if(name != nil)
if((name = pathlast(c->path)) != nil)
r = dirsetname(name, strlen(name), s, r, l);
poperror();
cclose(c);
return r;
@ -1330,12 +1331,10 @@ packoldstat(uchar *buf, Dir *d)
uintptr
sys_stat(va_list list)
{
static char old[] = "old stat system call - recompile";
char *name;
uchar *s;
Chan *c;
uint l;
uchar *s, buf[128]; /* old DIRLEN plus a little should be plenty */
char strs[128], *name;
Dir d;
Dir *d;
name = va_arg(list, char*);
s = va_arg(list, uchar*);
@ -1346,18 +1345,16 @@ sys_stat(va_list list)
cclose(c);
nexterror();
}
l = devtab[c->type]->stat(c, buf, sizeof buf);
/* buf contains a new stat buf; convert to old. yuck. */
if(l <= BIT16SZ) /* buffer too small; time to face reality */
error(old);
name = pathlast(c->path);
if(name != nil)
l = dirsetname(name, strlen(name), buf, l, sizeof buf);
l = convM2D(buf, l, &d, strs);
if(l == 0)
error(old);
packoldstat(s, &d);
d = dirchanstat(c);
if(waserror()){
free(d);
nexterror();
}
if((name = pathlast(c->path)) != nil)
d->name = name;
packoldstat(s, d);
poperror();
free(d);
poperror();
cclose(c);
return 0;
@ -1366,13 +1363,10 @@ sys_stat(va_list list)
uintptr
sys_fstat(va_list list)
{
static char old[] = "old fstat system call - recompile";
Chan *c;
char *name;
uint l;
uchar *s, buf[128]; /* old DIRLEN plus a little should be plenty */
char strs[128];
Dir d;
uchar *s;
Chan *c;
Dir *d;
int fd;
fd = va_arg(list, int);
@ -1383,18 +1377,16 @@ sys_fstat(va_list list)
cclose(c);
nexterror();
}
l = devtab[c->type]->stat(c, buf, sizeof buf);
/* buf contains a new stat buf; convert to old. yuck. */
if(l <= BIT16SZ) /* buffer too small; time to face reality */
error(old);
name = pathlast(c->path);
if(name != nil)
l = dirsetname(name, strlen(name), buf, l, sizeof buf);
l = convM2D(buf, l, &d, strs);
if(l == 0)
error(old);
packoldstat(s, &d);
d = dirchanstat(c);
if(waserror()){
free(d);
nexterror();
}
if((name = pathlast(c->path)) != nil)
d->name = name;
packoldstat(s, d);
poperror();
free(d);
poperror();
cclose(c);
return 0;