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Add support for closing/renumbering preopen fds #2578

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Merged
wenyongh merged 1 commit into from
Sep 26, 2023
Merged

Add support for closing/renumbering preopen fds #2578

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152 changes: 108 additions & 44 deletions core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/posix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -339,7 +339,7 @@ fd_prestats_init(struct fd_prestats *pt)

// Grows the preopened resource table to a required lower bound and a
// minimum number of free preopened resource table entries.
static bool
static __wasi_errno_t
fd_prestats_grow(struct fd_prestats *pt, size_t min, size_t incr)
REQUIRES_EXCLUSIVE(pt->lock)
{
Expand All @@ -353,7 +353,7 @@ fd_prestats_grow(struct fd_prestats *pt, size_t min, size_t incr)
struct fd_prestat *prestats =
wasm_runtime_malloc((uint32)(sizeof(*prestats) * size));
if (prestats == NULL)
return false;
return __WASI_ENOMEM;

if (pt->prestats && pt->size > 0) {
bh_memcpy_s(prestats, (uint32)(sizeof(*prestats) * size),
Expand All @@ -369,27 +369,39 @@ fd_prestats_grow(struct fd_prestats *pt, size_t min, size_t incr)
pt->prestats = prestats;
pt->size = size;
}
return true;
return __WASI_ESUCCESS;
}

// Inserts a preopened resource record into the preopened resource table.
bool
fd_prestats_insert(struct fd_prestats *pt, const char *dir, __wasi_fd_t fd)
static __wasi_errno_t
fd_prestats_insert_locked(struct fd_prestats *pt, const char *dir,
__wasi_fd_t fd)
{
// Grow the preopened resource table if needed.
rwlock_wrlock(&pt->lock);
if (!fd_prestats_grow(pt, fd, 1)) {
rwlock_unlock(&pt->lock);
return false;
__wasi_errno_t error = fd_prestats_grow(pt, fd, 1);

if (error != __WASI_ESUCCESS) {
return error;
}

pt->prestats[fd].dir = bh_strdup(dir);
rwlock_unlock(&pt->lock);

if (pt->prestats[fd].dir == NULL)
return false;
return __WASI_ENOMEM;

return true;
return __WASI_ESUCCESS;
}

// Inserts a preopened resource record into the preopened resource table.
bool
fd_prestats_insert(struct fd_prestats *pt, const char *dir, __wasi_fd_t fd)
{
rwlock_wrlock(&pt->lock);

__wasi_errno_t error = fd_prestats_insert_locked(pt, dir, fd);

rwlock_unlock(&pt->lock);

return error == __WASI_ESUCCESS;
}

// Looks up a preopened resource table entry by number.
Expand All @@ -408,6 +420,24 @@ fd_prestats_get_entry(struct fd_prestats *pt, __wasi_fd_t fd,
return 0;
}

// Remove a preopened resource record from the preopened resource table by
// number
static __wasi_errno_t
fd_prestats_remove_entry(struct fd_prestats *pt, __wasi_fd_t fd)
{
// Test for file descriptor existence.
if (fd >= pt->size)
return __WASI_EBADF;
struct fd_prestat *prestat = &pt->prestats[fd];

if (prestat->dir != NULL) {
wasm_runtime_free((void *)prestat->dir);
prestat->dir = NULL;
}

return __WASI_ESUCCESS;
}

struct fd_object {
struct refcount refcount;
__wasi_filetype_t type;
Expand Down Expand Up @@ -835,35 +865,36 @@ __wasi_errno_t
wasmtime_ssp_fd_close(wasm_exec_env_t exec_env, struct fd_table *curfds,
struct fd_prestats *prestats, __wasi_fd_t fd)
{
// Don't allow closing a pre-opened resource.
// TODO: Eventually, we do want to permit this, once libpreopen in
// userspace is capable of removing entries from its tables as well.
{
rwlock_rdlock(&prestats->lock);
struct fd_prestat *prestat;
__wasi_errno_t error = fd_prestats_get_entry(prestats, fd, &prestat);
rwlock_unlock(&prestats->lock);
if (error == 0) {
return __WASI_ENOTSUP;
}
}

// Validate the file descriptor.
struct fd_table *ft = curfds;
rwlock_wrlock(&ft->lock);
rwlock_wrlock(&prestats->lock);

struct fd_entry *fe;
__wasi_errno_t error = fd_table_get_entry(ft, fd, 0, 0, &fe);
if (error != 0) {
rwlock_unlock(&prestats->lock);
rwlock_unlock(&ft->lock);
return error;
}

// Remove it from the file descriptor table.
struct fd_object *fo;
fd_table_detach(ft, fd, &fo);

// Remove it from the preopened resource table if it exists
error = fd_prestats_remove_entry(prestats, fd);

rwlock_unlock(&prestats->lock);
rwlock_unlock(&ft->lock);
fd_object_release(exec_env, fo);
return 0;

// Ignore the error if there is no preopen associated with this fd
if (error == __WASI_EBADF) {
return __WASI_ESUCCESS;
}

return error;
}

// Look up a file descriptor object in a locked file descriptor table
Expand Down Expand Up @@ -1079,33 +1110,21 @@ wasmtime_ssp_fd_renumber(wasm_exec_env_t exec_env, struct fd_table *curfds,
struct fd_prestats *prestats, __wasi_fd_t from,
__wasi_fd_t to)
{
// Don't allow renumbering over a pre-opened resource.
// TODO: Eventually, we do want to permit this, once libpreopen in
// userspace is capable of removing entries from its tables as well.
{
rwlock_rdlock(&prestats->lock);
struct fd_prestat *prestat;
__wasi_errno_t error = fd_prestats_get_entry(prestats, to, &prestat);
if (error != 0) {
error = fd_prestats_get_entry(prestats, from, &prestat);
}
rwlock_unlock(&prestats->lock);
if (error == 0) {
return __WASI_ENOTSUP;
}
}

struct fd_table *ft = curfds;
rwlock_wrlock(&ft->lock);
rwlock_wrlock(&prestats->lock);

struct fd_entry *fe_from;
__wasi_errno_t error = fd_table_get_entry(ft, from, 0, 0, &fe_from);
if (error != 0) {
rwlock_unlock(&prestats->lock);
rwlock_unlock(&ft->lock);
return error;
}
struct fd_entry *fe_to;
error = fd_table_get_entry(ft, to, 0, 0, &fe_to);
if (error != 0) {
rwlock_unlock(&prestats->lock);
rwlock_unlock(&ft->lock);
return error;
}
Expand All @@ -1122,8 +1141,53 @@ wasmtime_ssp_fd_renumber(wasm_exec_env_t exec_env, struct fd_table *curfds,
fd_object_release(exec_env, fo);
--ft->used;

// Handle renumbering of any preopened resources
struct fd_prestat *prestat_from;
__wasi_errno_t prestat_from_error =
fd_prestats_get_entry(prestats, from, &prestat_from);

struct fd_prestat *prestat_to;
__wasi_errno_t prestat_to_error =
fd_prestats_get_entry(prestats, to, &prestat_to);

// Renumbering over two preopened resources.
if (prestat_from_error == __WASI_ESUCCESS
&& prestat_to_error == __WASI_ESUCCESS) {
(void)fd_prestats_remove_entry(prestats, to);

error = fd_prestats_insert_locked(prestats, prestat_from->dir, to);

if (error == __WASI_ESUCCESS) {
(void)fd_prestats_remove_entry(prestats, from);
}
else {
(void)fd_prestats_remove_entry(prestats, to);
}
}
// Renumbering from a non-preopened fd to a preopened fd. In this case, we
// can't a keep the destination fd entry in the preopened table so remove
// it entirely.
else if (prestat_from_error != __WASI_ESUCCESS
&& prestat_to_error == __WASI_ESUCCESS) {
(void)fd_prestats_remove_entry(prestats, to);
}
// Renumbering from a preopened fd to a non-preopened fd
else if (prestat_from_error == __WASI_ESUCCESS
&& prestat_to_error != __WASI_ESUCCESS) {
error = fd_prestats_insert_locked(prestats, prestat_from->dir, to);

if (error == __WASI_ESUCCESS) {
(void)fd_prestats_remove_entry(prestats, from);
}
else {
(void)fd_prestats_remove_entry(prestats, to);
}
}

rwlock_unlock(&prestats->lock);
rwlock_unlock(&ft->lock);
return 0;

return error;
}

__wasi_errno_t
Expand Down