From 59cb2d02a85a806884a99e39d7b1e5d4d35c129e Mon Sep 17 00:00:00 2001
From: ridiculousfish <corydoras@ridiculousfish.com>
Date: Mon, 18 Feb 2019 13:11:01 -0800
Subject: [PATCH] Only inherit a PWD if it resolves to "."

Fixes #5647
---
 src/env.cpp  | 12 +++++++-----
 tests/cd.in  | 14 ++++++++++++++
 tests/cd.out |  2 ++
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/env.cpp b/src/env.cpp
index 5b840859a..6da436aba 100644
--- a/src/env.cpp
+++ b/src/env.cpp
@@ -1014,11 +1014,13 @@ void env_init(const struct config_paths_t *paths /* or NULL */) {
     }
 
     // initialize the PWD variable if necessary
-    // Note we may inherit a virtual PWD that doesn't match what getcwd would return; respect that.
-    // Note we treat PWD as read-only so it was not set in vars.
-    const char *incoming_pwd = getenv("PWD");
-    if (incoming_pwd && incoming_pwd[0]) {
-        vars.set_one(L"PWD",  ENV_EXPORT | ENV_GLOBAL, str2wcstring(incoming_pwd));
+    // Note we may inherit a virtual PWD that doesn't match what getcwd would return; respect that
+    // if and only if it matches getcwd (#5647). Note we treat PWD as read-only so it was not set in
+    // vars.
+    const char *incoming_pwd_cstr = getenv("PWD");
+    wcstring incoming_pwd = incoming_pwd_cstr ? str2wcstring(incoming_pwd_cstr) : wcstring{};
+    if (!incoming_pwd.empty() && paths_are_same_file(incoming_pwd, L".")) {
+        vars.set_one(L"PWD", ENV_EXPORT | ENV_GLOBAL, incoming_pwd);
     } else {
         vars.set_pwd_from_getcwd();
     }
diff --git a/tests/cd.in b/tests/cd.in
index a537b1ea8..2d02d269c 100644
--- a/tests/cd.in
+++ b/tests/cd.in
@@ -47,8 +47,22 @@ mkdir -p $base/realhome
 set fish_path $PWD/../test/root/bin/fish
 ln -s $base/realhome $base/linkhome
 cd $base/linkhome
+set -l real_getcwd (pwd -P)
 env HOME=$base/linkhome $fish_path -c 'echo PWD is $PWD'
 
+# Do not inherit a virtual PWD that fails to resolve to getcwd (#5647)
+
+env HOME=$base/linkhome PWD=/tmp $fish_path -c 'echo $PWD' | read output_pwd
+test (realpath $output_pwd) = $real_getcwd
+and echo "BogusPWD test 1 succeeded"
+or echo "BogusPWD test 1 failed: $output_pwd vs $real_getcwd"
+
+env HOME=$base/linkhome PWD=/path/to/nowhere $fish_path -c 'echo $PWD' | read output_pwd
+test (realpath $output_pwd) = $real_getcwd
+and echo "BogusPWD test 2 succeeded"
+or echo "BogusPWD test 2 failed: $output_pwd vs $real_getcwd"
+
+
 # cd back before removing the test directory again.
 cd $oldpwd
 rm -Rf $base
diff --git a/tests/cd.out b/tests/cd.out
index 73081263d..8fd581f17 100644
--- a/tests/cd.out
+++ b/tests/cd.out
@@ -21,3 +21,5 @@ cd:
 ####################
 # Virtual PWD inheritance
 PWD is /tmp/cdcomp_test/linkhome
+BogusPWD test 1 succeeded
+BogusPWD test 2 succeeded