[newlib-cygwin/cygwin-3_4-branch] Cygwin: cwd: avoid releasing the cwdstuff SRW Lock twice

Corinna Vinschen corinna@sourceware.org
Tue Oct 31 10:27:07 GMT 2023


commit f0c90d3a8aa4409608abe76e035eab5919133a61
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Mon Oct 30 19:40:31 2023 +0100
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Tue Oct 31 10:52:02 2023 +0100

    Cygwin: cwd: avoid releasing the cwdstuff SRW Lock twice
    cwdstuff::set has a code snippet handling the case where a process
    can't create a handle to a directory, e. g., due to permissions.
    Commit 88443b0a22589 ("cwdstuff: Don't leave from setting the CWD
    prematurely on init") introduced a special case to handle this
    situation at process initialization. It also introduces an early
    mutex release, which is not required, but ok, because we're in the
    init phase. Releasing the mutex twice is no problem since the mutexes
    are recursive.
    Fast forward to commit 0819679a7a210 ("Cygwin: cwd: use SRWLOCK
    instead of muto"). The mechanical change from a recursive mutex
    to a non-recursive SRWLOCK failed to notice that this very specific
    situation will release the SRWLOCK twice.
    Remove the superfluous release action. While at it, don't set dir to
    NULL, but h, since dir will get the value of h anyway later on.
    Setting h to NULL may not be necessary, but better safe than sorry.
    Reported-by: tryandbuy >tryandbuy@proton.me>
    Fixes: 88443b0a22589 ("cwdstuff: Don't leave from setting the CWD prematurely on init")
    Fixes: 0819679a7a210 ("Cygwin: cwd: use SRWLOCK instead of muto")
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

 winsup/cygwin/path.cc        | 3 +--
 winsup/cygwin/release/3.4.10 | 3 +++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index e788c7d60e03..5ad9e201f74e 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -4942,10 +4942,9 @@ cwdstuff::set (path_conv *nat_cwd, const char *posix_cwd)
 			GetCurrentProcess (), &h, 0, TRUE, 0))
-	      release_write ();
 	      if (peb.ProcessParameters->CurrentDirectoryHandle)
 		debug_printf ("...and DuplicateHandle failed with %E.");
-	      dir = NULL;
+	      h = NULL;
diff --git a/winsup/cygwin/release/3.4.10 b/winsup/cygwin/release/3.4.10
index f34b131b32ae..c75283991461 100644
--- a/winsup/cygwin/release/3.4.10
+++ b/winsup/cygwin/release/3.4.10
@@ -3,3 +3,6 @@ Bug Fixes
 - Fix missing term in __cpuset_zero_s() prototoype in sys/cpuset.h.
   Addresses: https://cygwin.com/pipermail/cygwin/2023-September/254423.html
+- Fix hang in process initialization if cwd is unreadable.
+  Addresses: https://cygwin.com/pipermail/cygwin/2023-October/254604.html

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