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[dfs][9pfs] fix: clamp server-controlled lengths to the received reply #11918

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[dfs][9pfs] fix: clamp server-controlled lengths to the received reply #11918

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0e377be
[dfs][9pfs] fix: clamp server-controlled lengths to the received reply
usualtreee Oct 22, 2026
d6dc08b
[dfs][9pfs] fix: validate error codes before table lookup
usualtreee Nov 2, 2026
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72 changes: 66 additions & 6 deletions components/dfs/dfs_v1/filesystems/9pfs/dfs_9pfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -367,7 +367,7 @@ rt_err_t dfs_9pfs_del_tag(struct p9_protocol *p9p)

static int p9_to_fs_err(int rc)
{
const int p9_err[] = {
const int p9_err[1 - P9_MSG_SIZE_TOO_BIG] = {
[0] = RT_EOK,
[-P9_ERROR] = -EIO,
[-P9_UNKNOWN_VERSION] = -ENOSYS,
Expand All @@ -384,6 +384,12 @@ static int p9_to_fs_err(int rc)
[-P9_MSG_SIZE_TOO_BIG] = -ENOSPC,
};

/* Unknown or positive result codes cannot index the error table. */
if (rc > 0 || rc < P9_MSG_SIZE_TOO_BIG)
{
return -EIO;
}

return p9_err[-rc];
}

Expand Down Expand Up @@ -547,7 +553,7 @@ rt_inline int p9_walk_subpath(struct p9_connection *conn, const char *path)

static int dfs_9pfs_open(struct dfs_file *fd)
{
int rc;
int rc = 0;
rt_uint32_t size;
rt_bool_t is_root;
struct p9_connection *conn;
Expand Down Expand Up @@ -682,7 +688,7 @@ static ssize_t dfs_9pfs_read(struct dfs_file *fd, void *buf, size_t count)
{
int rc;
size_t tcount = 0;
rt_uint32_t max_count, set, size, got;
rt_uint32_t max_count, set, size, got, rx_size = 0;
struct p9_file *p9f = fd->vnode->data;
struct p9_connection *conn = p9f->connection;

Expand All @@ -704,10 +710,26 @@ static ssize_t dfs_9pfs_read(struct dfs_file *fd, void *buf, size_t count)
size = put_value32(conn, size, set);
put_tx_value32_of(conn, P9_MSG_SIZE, size);

if (!(rc = p9_transaction(conn, size, RT_NULL)))
if (!(rc = p9_transaction(conn, size, &rx_size)))
{
if (rx_size < P9_MSG_READ_DATA)
{
/* the reply does not even hold the count field */
tcount = p9_to_fs_err(P9_READ_UNEXPECTED_DATA);
break;
}

got = get_rx_value32_of(conn, P9_MSG_READ_COUNT);

/*
* Never trust the wire: the file data must fit into the data
* that was actually received.
*/
if (got > rx_size - P9_MSG_READ_DATA)
{
got = rx_size - P9_MSG_READ_DATA;
}

if (got == 0)
{
break;
Expand Down Expand Up @@ -824,7 +846,7 @@ static int dfs_9pfs_getdents(struct dfs_file *fd, struct dirent *dirp, uint32_t
{
int rc;
rt_uint64_t off;
rt_uint32_t ret, end, stat_size, size;
rt_uint32_t ret, end, stat_size, size, rx_size = 0;
struct p9_file *p9f = fd->vnode->data;
struct p9_connection *conn = p9f->connection;

Expand All @@ -849,23 +871,56 @@ static int dfs_9pfs_getdents(struct dfs_file *fd, struct dirent *dirp, uint32_t
size = put_value32(conn, size, fd->vnode->size);
put_tx_value32_of(conn, P9_MSG_SIZE, size);

if (!(rc = p9_transaction(conn, size, RT_NULL)))
if (!(rc = p9_transaction(conn, size, &rx_size)))
{
if (rx_size < P9_MSG_READ_DATA)
{
/* the reply does not even hold the count field */
rt_mutex_release(&conn->lock);
return -EIO;
}

ret = get_rx_value32_of(conn, P9_MSG_READ_COUNT);

/*
* Never trust the wire: the directory entries must fit into the
* data that was actually received.
*/
if (ret > rx_size - P9_MSG_READ_DATA)
{
ret = rx_size - P9_MSG_READ_DATA;
}
off = P9_MSG_READ_DATA - P9_MSG_STAT_SIZE;

for (int i = 0; (rt_int32_t)ret > 0; off += stat_size, ret -= stat_size, ++i)
{
if (ret < sizeof(rt_uint16_t))
{
/* not even the size field of the next record is left */
break;
}

/*
* size[2] type[2] dev[4] qid[1+4+8] mode[4] atime[4] mtime[4] length[8]
*/
stat_size = get_rx_value16_of(conn, off + P9_MSG_STAT_SIZE) + sizeof(rt_uint16_t);
if (stat_size > ret)
{
/* the record overruns the received data */
break;
}

if (i < fd->pos)
{
continue;
}

if (stat_size < P9_MSG_STAT_NAME_LEN - P9_MSG_STAT_SIZE + sizeof(rt_uint16_t))
{
/* the record cannot hold the fields up to the name length */
break;
}

if (get_rx_value16_of(conn, off + P9_MSG_STAT_TYPE) & P9_STAT_MODE_DIR)
{
dirp->d_type = DT_DIR;
Expand All @@ -886,6 +941,11 @@ static int dfs_9pfs_getdents(struct dfs_file *fd, struct dirent *dirp, uint32_t
* n_muid[4]
*/
dirp->d_namlen = get_rx_value16_of(conn, off + P9_MSG_STAT_NAME_LEN);
if (P9_MSG_STAT_NAME - P9_MSG_STAT_SIZE + dirp->d_namlen > stat_size)
{
/* the name overruns this record */
break;
}
dirp->d_reclen = (rt_uint16_t)sizeof(struct dirent);
rt_strncpy(dirp->d_name,
(void *)conn->rx_buffer + off + P9_MSG_STAT_NAME,
Expand Down
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