From 394984db9c8727f953b3499e6378d999a9c2dce4 Mon Sep 17 00:00:00 2001
From: barneygale <barney.gale@gmail.com>
Date: Tue, 2 Apr 2024 20:28:39 +0100
Subject: [PATCH 1/3] GH-114847: Raise FileNotFoundError when getcwd() returns
 '(unreachable)'

On Linux >= 2.6.36 with glibc < 2.27, `getcwd()` can return a relative
pathname starting with '(unreachable)'. We detect this and fail with
ENOENT, matching new glibc behaviour.
---
 .../2024-04-02-20-30-12.gh-issue-114848.YX4pEc.rst  |  2 ++
 Modules/posixmodule.c                               | 13 +++++++++++++
 2 files changed, 15 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2024-04-02-20-30-12.gh-issue-114848.YX4pEc.rst

diff --git a/Misc/NEWS.d/next/Library/2024-04-02-20-30-12.gh-issue-114848.YX4pEc.rst b/Misc/NEWS.d/next/Library/2024-04-02-20-30-12.gh-issue-114848.YX4pEc.rst
new file mode 100644
index 00000000000000..30b1a50976f52d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-04-02-20-30-12.gh-issue-114848.YX4pEc.rst
@@ -0,0 +1,2 @@
+Raise :exc:`FileNotFoundError` when ``getcwd()`` returns '(unreachable)',
+which can happen on Linux >= 2.6.36 with glibc < 2.27.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index a4b635ef5bf629..ec93359c0c697e 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -4098,6 +4098,19 @@ posix_getcwd(int use_bytes)
         PyMem_RawFree(buf);
         return NULL;
     }
+#ifdef __linux__
+    if (buf[0] != '/') {
+        /*
+         * On Linux >= 2.6.36 with glibc < 2.27, getcwd() can return a
+         * relative pathname starting with '(unreachable)'. We detect this
+         * and fail with ENOENT, matching newer glibc behaviour.
+         */
+        errno = ENOENT;
+        posix_error();
+        PyMem_RawFree(buf);
+        return NULL;
+    }
+#endif
 
     PyObject *obj;
     if (use_bytes) {

From bec3b2cdb3e66ba429c9776c870571684ff80d34 Mon Sep 17 00:00:00 2001
From: barneygale <barney.gale@gmail.com>
Date: Tue, 2 Apr 2024 21:40:37 +0100
Subject: [PATCH 2/3] Add getcwd() result to OSError

---
 Modules/posixmodule.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index ec93359c0c697e..5c1e697908e44a 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -4098,6 +4098,14 @@ posix_getcwd(int use_bytes)
         PyMem_RawFree(buf);
         return NULL;
     }
+
+    PyObject *obj;
+    if (use_bytes) {
+        obj = PyBytes_FromStringAndSize(buf, strlen(buf));
+    }
+    else {
+        obj = PyUnicode_DecodeFSDefault(buf);
+    }
 #ifdef __linux__
     if (buf[0] != '/') {
         /*
@@ -4106,19 +4114,11 @@ posix_getcwd(int use_bytes)
          * and fail with ENOENT, matching newer glibc behaviour.
          */
         errno = ENOENT;
-        posix_error();
+        path_object_error(obj);
         PyMem_RawFree(buf);
         return NULL;
     }
 #endif
-
-    PyObject *obj;
-    if (use_bytes) {
-        obj = PyBytes_FromStringAndSize(buf, strlen(buf));
-    }
-    else {
-        obj = PyUnicode_DecodeFSDefault(buf);
-    }
     PyMem_RawFree(buf);
 
     return obj;

From c11f3a8be10516257f816ef5ffc002f99acbfbbf Mon Sep 17 00:00:00 2001
From: Barney Gale <barney.gale@gmail.com>
Date: Wed, 3 Apr 2024 16:07:14 +0100
Subject: [PATCH 3/3] Update Modules/posixmodule.c

Co-authored-by: Petr Viktorin <encukou@gmail.com>
---
 Modules/posixmodule.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 5c1e697908e44a..fcac3dbe3553ef 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -4119,6 +4119,7 @@ posix_getcwd(int use_bytes)
         return NULL;
     }
 #endif
+    assert(buf[0] == '/');
     PyMem_RawFree(buf);
 
     return obj;