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Fix fd_readdir to properly truncate directory entry names.

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Previously, `fd_readdir` was truncating directory entry names based on the
calculation of `min(name_len, buf_len - bufused)`, but `bufused` was not being
updated after writing in the `dirent` structure to the buffer.

This allowed `bufused` to be incremented beyond `buf_len` and returned as the
number of bytes written to the buffer, which is invalid.

This fix adjusts `bufused` when the buffer is written to for the `dirent` so
that name truncation happens as expected.

Fixes #2618.
This commit is contained in:
Peter Huene
2021-01-28 12:39:40 -08:00
parent d1c1cb6a25
commit 4632228b35
1 changed files with 2 additions and 3 deletions
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5
crates/wasi-common/src/snapshots/wasi_snapshot_preview1.rs
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@@ -304,7 +304,6 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
let dirent_len: types::Size = dirent_raw.len().try_into()?; let dirent_len: types::Size = dirent_raw.len().try_into()?;
let name_raw = name.as_bytes(); let name_raw = name.as_bytes();
let name_len = name_raw.len().try_into()?; let name_len = name_raw.len().try_into()?;
let offset = dirent_len.checked_add(name_len).ok_or(Error::Overflow)?;
// Copy as many bytes of the dirent as we can, up to the end of the buffer. // Copy as many bytes of the dirent as we can, up to the end of the buffer.
let dirent_copy_len = min(dirent_len, buf_len - bufused); let dirent_copy_len = min(dirent_len, buf_len - bufused);
@@ -318,6 +317,7 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
} }
buf = buf.add(dirent_copy_len)?; buf = buf.add(dirent_copy_len)?;
bufused += dirent_copy_len;
// Copy as many bytes of the name as we can, up to the end of the buffer. // Copy as many bytes of the name as we can, up to the end of the buffer.
let name_copy_len = min(name_len, buf_len - bufused); let name_copy_len = min(name_len, buf_len - bufused);
@@ -331,8 +331,7 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
} }
buf = buf.add(name_copy_len)?; buf = buf.add(name_copy_len)?;
bufused += name_copy_len;
bufused += offset;
} }
Ok(bufused) Ok(bufused)