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std.Progress: truncate IPC data exceeding preallocated buffers

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This accomplishes 2 things simultaneously:

1. Don't trust child process data; if the data is outside the expected
   range, ignore the data.
2. If there is too much data to fit in the preallocated buffers, drop
   the data.
This commit is contained in:
Andrew Kelley 2024-05-26 16:05:38 -07:00
parent 807b613f71
commit 52ed54d1e7
1 changed files with 27 additions and 18 deletions
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45
lib/std/Progress.zig
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@ -593,9 +593,9 @@ var ipc_metadata_len: u16 = 0;
const SavedMetadata = struct {
ipc_fd: u16,
main_index: u16,
start_index: u16,
nodes_len: u16,
main_index: u8,
start_index: u8,
nodes_len: u8,
fn getIpcFd(metadata: SavedMetadata) posix.fd_t {
return if (builtin.os.tag == .windows)
@ -677,11 +677,13 @@ fn serializeIpc(start_serialized_len: usize, serialized_buffer: *Serialized.Buff
};
};
const nodes_len: u8 = @intCast(@min(parents.len - 1, serialized_buffer.storage.len - serialized_len));
// Remember in case the pipe is empty on next update.
ipc_metadata[ipc_metadata_len] = .{
.ipc_fd = SavedMetadata.setIpcFd(fd),
.start_index = @intCast(serialized_len),
.nodes_len = @intCast(parents.len),
.nodes_len = nodes_len,
.main_index = @intCast(main_index),
};
ipc_metadata_len += 1;
@ -690,24 +692,26 @@ fn serializeIpc(start_serialized_len: usize, serialized_buffer: *Serialized.Buff
copyRoot(main_storage, &storage[0]);
// Copy the rest of the tree to the end.
@memcpy(serialized_buffer.storage[serialized_len..][0 .. storage.len - 1], storage[1..]);
@memcpy(serialized_buffer.storage[serialized_len..][0..nodes_len], storage[1..][0..nodes_len]);
// Patch up parent pointers taking into account how the subtree is mounted.
serialized_buffer.parents[serialized_len] = .none;
for (serialized_buffer.parents[serialized_len..][0 .. parents.len - 1], parents[1..]) |*dest, p| {
for (serialized_buffer.parents[serialized_len..][0..nodes_len], parents[1..][0..nodes_len]) |*dest, p| {
dest.* = switch (p) {
// Fix bad data so the rest of the code does not see `unused`.
.none, .unused => .none,
// Root node is being mounted here.
@as(Node.Parent, @enumFromInt(0)) => @enumFromInt(main_index),
// Other nodes mounted at the end.
// TODO check for bad data pointing outside the expected range
_ => |off| @enumFromInt(serialized_len + @intFromEnum(off) - 1),
// Don't trust child data; if the data is outside the expected range, ignore the data.
// This also handles the case when data was truncated.
_ => |off| if (@intFromEnum(off) > nodes_len)
.none
else
@enumFromInt(serialized_len + @intFromEnum(off) - 1),
};
}
serialized_len += storage.len - 1;
serialized_len += nodes_len;
}
// Save a copy in case any pipes are empty on the next update.
@ -753,7 +757,7 @@ fn useSavedIpcData(
};
const start_index = saved_metadata.start_index;
const nodes_len = saved_metadata.nodes_len;
const nodes_len = @min(saved_metadata.nodes_len, serialized_buffer.storage.len - start_serialized_len);
const old_main_index = saved_metadata.main_index;
ipc_metadata[ipc_metadata_len] = .{
@ -764,8 +768,8 @@ fn useSavedIpcData(
};
ipc_metadata_len += 1;
const parents = parents_copy[start_index..][0 .. nodes_len - 1];
const storage = storage_copy[start_index..][0 .. nodes_len - 1];
const parents = parents_copy[start_index..][0..nodes_len];
const storage = storage_copy[start_index..][0..nodes_len];
copyRoot(main_storage, &storage_copy[old_main_index]);
@ -774,10 +778,15 @@ fn useSavedIpcData(
for (serialized_buffer.parents[start_serialized_len..][0..parents.len], parents) |*dest, p| {
dest.* = switch (p) {
.none, .unused => .none,
_ => |prev| @enumFromInt(if (@intFromEnum(prev) == old_main_index)
main_index
else
@intFromEnum(prev) - start_index + start_serialized_len),
_ => |prev| d: {
if (@intFromEnum(prev) == old_main_index) {
break :d @enumFromInt(main_index);
} else if (@intFromEnum(prev) > nodes_len) {
break :d .none;
} else {
break :d @enumFromInt(@intFromEnum(prev) - start_index + start_serialized_len);
}
},
};
}