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9pfs: handle walk of ".." in the root directory 

The 9P spec at http://man.cat-v.org/plan_9/5/intro says:

All directories must support walks to the directory .. (dot-dot) meaning
parent directory, although by convention directories contain no explicit
entry for .. or . (dot).  The parent of the root directory of a server's
tree is itself.

This means that a client cannot walk further than the root directory
exported by the server. In other words, if the client wants to walk
"/.." or "/foo/../..", the server should answer like the request was
to walk "/".

This patch just does that:
- we cache the QID of the root directory at attach time
- during the walk we compare the QID of each path component with the root
  QID to detect if we're in a "/.." situation
- if so, we skip the current component and go to the next one

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Greg Kurz 2016-08-30 17:02:27 +02:00 committed by Peter Maydell
parent 805b5d98c6
commit 56f101ecce
2 changed files with 32 additions and 9 deletions
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40
hw/9pfs/9p.c
View File

@ -1010,6 +1010,7 @@ static void v9fs_attach(void *opaque)
goto out;
}
err += offset;
memcpy(&s->root_qid, &qid, sizeof(qid));
trace_v9fs_attach_return(pdu->tag, pdu->id,
qid.type, qid.version, qid.path);
/*
@ -1261,6 +1262,14 @@ static bool name_is_illegal(const char *name)
return !*name || strchr(name, '/') != NULL;
}
static bool not_same_qid(const V9fsQID *qid1, const V9fsQID *qid2)
{
return
qid1->type != qid2->type ||
qid1->version != qid2->version ||
qid1->path != qid2->path;
}
static void v9fs_walk(void *opaque)
{
int name_idx;
@ -1276,6 +1285,7 @@ static void v9fs_walk(void *opaque)
V9fsFidState *newfidp = NULL;
V9fsPDU *pdu = opaque;
V9fsState *s = pdu->s;
V9fsQID qid;
err = pdu_unmarshal(pdu, offset, "ddw", &fid, &newfid, &nwnames);
if (err < 0) {
@ -1309,6 +1319,12 @@ static void v9fs_walk(void *opaque)
err = -ENOENT;
goto out_nofid;
}
err = fid_to_qid(pdu, fidp, &qid);
if (err < 0) {
goto out;
}
v9fs_path_init(&dpath);
v9fs_path_init(&path);
/*
@ -1318,16 +1334,22 @@ static void v9fs_walk(void *opaque)
v9fs_path_copy(&dpath, &fidp->path);
v9fs_path_copy(&path, &fidp->path);
for (name_idx = 0; name_idx < nwnames; name_idx++) {
err = v9fs_co_name_to_path(pdu, &dpath, wnames[name_idx].data, &path);
if (err < 0) {
goto out;
if (not_same_qid(&pdu->s->root_qid, &qid) ||
strcmp("..", wnames[name_idx].data)) {
err = v9fs_co_name_to_path(pdu, &dpath, wnames[name_idx].data,
&path);
if (err < 0) {
goto out;
}
err = v9fs_co_lstat(pdu, &path, &stbuf);
if (err < 0) {
goto out;
}
stat_to_qid(&stbuf, &qid);
v9fs_path_copy(&dpath, &path);
}
err = v9fs_co_lstat(pdu, &path, &stbuf);
if (err < 0) {
goto out;
}
stat_to_qid(&stbuf, &qids[name_idx]);
v9fs_path_copy(&dpath, &path);
memcpy(&qids[name_idx], &qid, sizeof(qid));
}
if (fid == newfid) {
BUG_ON(fidp->fid_type != P9_FID_NONE);

1
hw/9pfs/9p.h
View File

@ -236,6 +236,7 @@ typedef struct V9fsState
int32_t root_fid;
Error *migration_blocker;
V9fsConf fsconf;
V9fsQID root_qid;
} V9fsState;
/* 9p2000.L open flags */