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portal: Use a GArray to store fds

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This will allow us to add additional mapping entries for fds to be
used internally by `flatpak run`, in particular --env-fd.

Defer the second pass through the fd array until the last possible
moment, so that any extra fds we want to add (like the --env-fd) have
already been added by then.

Helps: flatpak/flatpak#4286
Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie
2021-05-21 13:38:18 +01:00
committed by Alexander Larsson
parent f2fbc75827
commit a09d07f085
1 changed files with 42 additions and 39 deletions
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81
portal/flatpak-portal.c
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@@ -253,7 +253,7 @@ typedef struct
typedef struct
{
FdMapEntry *fd_map;
int fd_map_len;
gsize fd_map_len;
int instance_id_fd;
gboolean set_tty;
int tty;
@@ -479,7 +479,7 @@ child_setup_func (gpointer user_data)
ChildSetupData *data = (ChildSetupData *) user_data;
FdMapEntry *fd_map = data->fd_map;
sigset_t set;
int i;
gsize i;
flatpak_close_fds_workaround (3);
@@ -760,7 +760,7 @@ handle_spawn (PortalFlatpak *object,
gsize i, j, n_fds, n_envs;
const gint *fds = NULL;
gint fds_len = 0;
g_autofree FdMapEntry *fd_map = NULL;
g_autoptr(GArray) fd_map = NULL;
g_auto(GStrv) env = NULL;
gint32 max_fd;
GKeyFile *app_info;
@@ -930,14 +930,13 @@ handle_spawn (PortalFlatpak *object,
n_fds = 0;
if (fds != NULL)
n_fds = g_variant_n_children (arg_fds);
fd_map = g_new0 (FdMapEntry, n_fds);
child_setup_data.fd_map = fd_map;
child_setup_data.fd_map_len = n_fds;
fd_map = g_array_sized_new (FALSE, FALSE, sizeof (FdMapEntry), n_fds);
max_fd = -1;
for (i = 0; i < n_fds; i++)
{
FdMapEntry fd_map_entry;
gint32 handle, dest_fd;
int handle_fd;
@@ -954,9 +953,10 @@ handle_spawn (PortalFlatpak *object,
handle_fd = fds[handle];
fd_map[i].to = dest_fd;
fd_map[i].from = handle_fd;
fd_map[i].final = fd_map[i].to;
fd_map_entry.to = dest_fd;
fd_map_entry.from = handle_fd;
fd_map_entry.final = fd_map_entry.to;
g_array_append_val (fd_map, fd_map_entry);
/* If stdin/out/err is a tty we try to set it as the controlling
tty for the app, this way we can use this to run in a terminal. */
@@ -968,36 +968,8 @@ handle_spawn (PortalFlatpak *object,
child_setup_data.tty = handle_fd;
}
max_fd = MAX (max_fd, fd_map[i].to);
max_fd = MAX (max_fd, fd_map[i].from);
}
/* We make a second pass over the fds to find if any "to" fd index
overlaps an already in use fd (i.e. one in the "from" category
that are allocated randomly). If a fd overlaps "to" fd then its
a caller issue and not our fault, so we ignore that. */
for (i = 0; i < n_fds; i++)
{
int to_fd = fd_map[i].to;
gboolean conflict = FALSE;
/* At this point we're fine with using "from" values for this
value (because we handle to==from in the code), or values
that are before "i" in the fd_map (because those will be
closed at this point when dup:ing). However, we can't
reuse a fd that is in "from" for j > i. */
for (j = i + 1; j < n_fds; j++)
{
int from_fd = fd_map[j].from;
if (from_fd == to_fd)
{
conflict = TRUE;
break;
}
}
if (conflict)
fd_map[i].to = ++max_fd;
max_fd = MAX (max_fd, fd_map_entry.to);
max_fd = MAX (max_fd, fd_map_entry.from);
}
/* TODO: Ideally we should let `flatpak run` inherit the portal's
@@ -1440,6 +1412,37 @@ handle_spawn (PortalFlatpak *object,
g_debug ("Starting: %s\n", cmd->str);
}
/* We make a second pass over the fds to find if any "to" fd index
overlaps an already in use fd (i.e. one in the "from" category
that are allocated randomly). If a fd overlaps "to" fd then its
a caller issue and not our fault, so we ignore that. */
for (i = 0; i < fd_map->len; i++)
{
int to_fd = g_array_index (fd_map, FdMapEntry, i).to;
gboolean conflict = FALSE;
/* At this point we're fine with using "from" values for this
value (because we handle to==from in the code), or values
that are before "i" in the fd_map (because those will be
closed at this point when dup:ing). However, we can't
reuse a fd that is in "from" for j > i. */
for (j = i + 1; j < fd_map->len; j++)
{
int from_fd = g_array_index(fd_map, FdMapEntry, j).from;
if (from_fd == to_fd)
{
conflict = TRUE;
break;
}
}
if (conflict)
g_array_index (fd_map, FdMapEntry, i).to = ++max_fd;
}
child_setup_data.fd_map = &g_array_index (fd_map, FdMapEntry, 0);
child_setup_data.fd_map_len = fd_map->len;
/* We use LEAVE_DESCRIPTORS_OPEN to work around dead-lock, see flatpak_close_fds_workaround */
if (!g_spawn_async_with_pipes (NULL,
(char **) flatpak_argv->pdata,