From dbb8069df56cb68ea1167b3bc0ceb66fa6c35d3f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bernhard=20=C3=9Cbelacker?= Date: Sat, 16 Nov 2024 18:09:50 +0100 Subject: [PATCH] Cygwin: check_dir_not_empty: Avoid leaving the allocated buffer. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The pointer pfni gets allocated the buffer at the begin, and is used in the NtQueryDirectoryFile call before the loops. In the loop the pointer pfni is also used as iterator. Therefore it holds no longer the initial buffer at the call to NtQueryDirectoryFile in the while conditition at the bottom. Fixes: 28fa2a72f8106 ("* syscalls.cc (check_dir_not_empty): Check surplus directory entries") Co-authored-by: Corinna Vinschen Signed-off-by: Bernhard Übelacker --- winsup/cygwin/release/3.5.5 | 3 +++ winsup/cygwin/syscalls.cc | 10 ++++++---- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/winsup/cygwin/release/3.5.5 b/winsup/cygwin/release/3.5.5 index 2ca4572db..3088f8682 100644 --- a/winsup/cygwin/release/3.5.5 +++ b/winsup/cygwin/release/3.5.5 @@ -33,3 +33,6 @@ Fixes: - Fix type of pthread_sigqueue() first parameter to match Linux. Addresses: https://cygwin.com/pipermail/cygwin/2024-September/256439.html + +- Fix potential stack corruption in rmdir() in a border case. + Addresses: https://cygwin.com/pipermail/cygwin/2024-November/256774.html diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc index df7d3a14e..433739cda 100644 --- a/winsup/cygwin/syscalls.cc +++ b/winsup/cygwin/syscalls.cc @@ -617,9 +617,10 @@ check_dir_not_empty (HANDLE dir, path_conv &pc) IO_STATUS_BLOCK io; const ULONG bufsiz = 3 * sizeof (FILE_NAMES_INFORMATION) + 3 * NAME_MAX * sizeof (WCHAR); - PFILE_NAMES_INFORMATION pfni = (PFILE_NAMES_INFORMATION) - alloca (bufsiz); - NTSTATUS status = NtQueryDirectoryFile (dir, NULL, NULL, 0, &io, pfni, + PFILE_NAMES_INFORMATION pfni_buf = (PFILE_NAMES_INFORMATION) + alloca (bufsiz); + PFILE_NAMES_INFORMATION pfni; + NTSTATUS status = NtQueryDirectoryFile (dir, NULL, NULL, 0, &io, pfni_buf, bufsiz, FileNamesInformation, FALSE, NULL, TRUE); if (!NT_SUCCESS (status)) @@ -631,6 +632,7 @@ check_dir_not_empty (HANDLE dir, path_conv &pc) int cnt = 1; do { + pfni = pfni_buf; while (pfni->NextEntryOffset) { if (++cnt > 2) @@ -677,7 +679,7 @@ check_dir_not_empty (HANDLE dir, path_conv &pc) pfni = (PFILE_NAMES_INFORMATION) ((caddr_t) pfni + pfni->NextEntryOffset); } } - while (NT_SUCCESS (NtQueryDirectoryFile (dir, NULL, NULL, 0, &io, pfni, + while (NT_SUCCESS (NtQueryDirectoryFile (dir, NULL, NULL, 0, &io, pfni_buf, bufsiz, FileNamesInformation, FALSE, NULL, FALSE))); return STATUS_SUCCESS;