utils.c: fix file_exists_at musl compatibility.

utils.c: file_exists_at: fallback to `fstatat` when `faccessat` fails with `EINVAL` (on musl).
.travis.yml: alpine test added.
main.c: reallocate path before appending.

Closes #174.

Signed-off-by: Max Goltzsche <max.goltzsche@gmail.com>

.dockerignore

@@ -0,0 +1,10 @@
+*
+
+!lib
+!m4
+!*.sh
+!*.ac
+!*.am
+!*.md
+!*.h
+!*.c

.travis.yml

@@ -26,7 +26,6 @@ addons:
       - parallel
 before_install:
   - docker pull fedora &
-  - docker build -t alpine-build -f Dockerfile.alpine .
   - (wget https://dl.google.com/go/go1.13.7.linux-amd64.tar.gz && tar xf go1.13.7.linux-amd64.tar.gz && sudo mv go /usr/local)
   - sudo mkdir -p /lower /upper /mnt
   - (cd /; sudo git clone https://github.com/amir73il/unionmount-testsuite.git)
@@ -44,6 +43,6 @@ script:
   - (cd /unionmount-testsuite; sudo FUSE_OVERLAYFS_DISABLE_OVL_WHITEOUT=1 unshare -m ./run --ov --fuse=fuse-overlayfs --xdev) || travis_terminate 1;
   - sudo tests/fedora-installs.sh || travis_terminate 1;
   - sudo tests/unlink.sh || travis_terminate 1;
+  - sudo tests/alpine.sh || travis_terminate 1;
   - (cd $GOPATH/src/github.com/containers/storage/tests; sudo JOBS=1 STORAGE_OPTION=overlay.mount_program=/sbin/fuse-overlayfs STORAGE_DRIVER=overlay unshare -m ./test_runner.bash) || travis_terminate 1;
   - (cd $GOPATH/src/github.com/containers/storage/tests; sudo JOBS=1 FUSE_OVERLAYFS_DISABLE_OVL_WHITEOUT=1 STORAGE_OPTION=overlay.mount_program=/sbin/fuse-overlayfs STORAGE_DRIVER=overlay unshare -m ./test_runner.bash) || travis_terminate 1;
-  - docker run --rm  -v $(pwd):/fuse-overlayfs alpine-build sh -c 'cd /fuse-overlayfs; ./autogen.sh && ./configure && make clean && make'

Dockerfile.alpine

@@ -1,2 +1,23 @@
 FROM alpine
-RUN apk add make gcc fuse3-dev libc-dev go-md2man linux-headers automake autoconf gettext
+WORKDIR /build
+RUN apk add git make gcc libc-dev musl-dev glib-static gettext eudev-dev \
+	linux-headers automake autoconf cmake meson ninja clang go-md2man
+
+RUN git clone https://github.com/libfuse/libfuse && \
+    cd libfuse && \
+    mkdir build && \
+    cd build && \
+    LDFLAGS="-lpthread -s -w -static" meson --prefix /usr -D default_library=static .. && \
+    ninja && \
+    ninja install
+
+COPY . /build/fuse-overlayfs
+RUN cd fuse-overlayfs && \
+    ./autogen.sh && \
+    LIBS="-ldl" LDFLAGS="-s -w -static" ./configure --prefix /usr && \
+    make clean && \
+    make && \
+    make install
+
+USER nobody
+ENTRYPOINT ["/usr/bin/fuse-overlayfs","-f"]

main.c

@@ -5231,6 +5231,9 @@ main (int argc, char *argv[])
       if (path == NULL)
         goto err_out1;
       mkdir (path, 0700);
+      path = realloc(path, strlen(path)+strlen("/work")+1);
+      if (!path)
+        error (EXIT_FAILURE, errno, "allocating workdir path");
       strcat (path, "/work");
       mkdir (path, 0700);
       free (lo.workdir);

tests/alpine.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+cd "$(dirname "$0")"
+
+set -ex
+
+docker build -t fuse-overlayfs:alpine -f ../Dockerfile.alpine ..
+
+docker run --privileged --rm --entrypoint /unlink.sh -w /tmp \
+	-e EXPECT_UMOUNT_STATUS=1 \
+	-v "$(pwd)/unlink.sh:/unlink.sh" fuse-overlayfs:alpine

tests/unlink.sh

@@ -1,6 +1,11 @@
 #!/bin/sh
 
-rm -rf lower upper workdir merged
+set -ex
+
+rm -rf unlink-test
+mkdir unlink-test
+
+cd unlink-test
 
 mkdir lower upper workdir merged
 
@@ -21,4 +26,4 @@ echo world >> merged/foo2
 grep hello merged/foo
 grep world merged/foo
 
-umount merged
+umount merged || [ $? -eq "${EXPECT_UMOUNT_STATUS:-0}" ]

utils.c

@@ -103,7 +103,12 @@ safe_openat (int dirfd, const char *pathname, int flags, mode_t mode)
 int
 file_exists_at (int dirfd, const char *pathname)
 {
-  return faccessat (dirfd, pathname, F_OK, AT_SYMLINK_NOFOLLOW|AT_EACCESS);
+  int ret = faccessat (dirfd, pathname, F_OK, AT_SYMLINK_NOFOLLOW|AT_EACCESS);
+  if (ret < 0 && errno == EINVAL) {
+    struct stat buf;
+    return fstatat (dirfd, pathname, &buf, AT_SYMLINK_NOFOLLOW);
+  }
+  return ret;
 }
 
 #ifdef HAVE_STATX