[PATCH 1/2] linux user: fixed proc myself execfd behaviour, added tests for proc myself fd

[PATCH 1/2] linux user: fixed proc myself execfd behaviour, added tests for proc myself fd

[Andrew Aladjev]

Signed-off-by: Andrew Aladjev <aladjev.andrew@gmail.com>
---
 linux-user/elfload.c             |  3 +-
 linux-user/main.c                | 11 ++++-
 linux-user/syscall.c             |  7 ++-
 tests/tcg/multiarch/linux-test.c | 85 ++++++++++++++++++++++++++++++++
 4 files changed, 101 insertions(+), 5 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index fe9dfe795d..353094da34 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2363,6 +2363,7 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
 
    IMAGE_NAME is the filename of the image, to use in error messages.
    IMAGE_FD is the open file descriptor for the image.
+   WARNING : IMAGE_FD won't be closed.
 
    BPRM_BUF is a copy of the beginning of the file; this of course
    contains the elf file header at offset 0.  It is assumed that this
@@ -2632,7 +2633,6 @@ static void load_elf_image(const char *image_name, int image_fd,
 
     mmap_unlock();
 
-    close(image_fd);
     return;
 
  exit_read:
@@ -2666,6 +2666,7 @@ static void load_elf_interp(const char *filename, struct image_info *info,
     }
 
     load_elf_image(filename, fd, info, NULL, bprm_buf);
+    close(fd);
     return;
 
  exit_perror:
diff --git a/linux-user/main.c b/linux-user/main.c
index 75c9785157..29b61d4a09 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -629,6 +629,7 @@ int main(int argc, char **argv, char **envp)
     int target_argc;
     int i;
     int ret;
+    int at_execfd;
     int execfd;
     int log_mask;
     unsigned long max_reserved_va;
@@ -690,13 +691,15 @@ int main(int argc, char **argv, char **envp)
 
     init_qemu_uname_release();
 
-    execfd = qemu_getauxval(AT_EXECFD);
-    if (execfd == 0) {
+    at_execfd = qemu_getauxval(AT_EXECFD);
+    if (at_execfd == 0) {
         execfd = open(exec_path, O_RDONLY);
         if (execfd < 0) {
             printf("Error while loading %s: %s\n", exec_path, strerror(errno));
             _exit(EXIT_FAILURE);
         }
+    } else {
+        execfd = at_execfd;
     }
 
     if (cpu_model == NULL) {
@@ -811,6 +814,10 @@ int main(int argc, char **argv, char **envp)
 
     ret = loader_exec(execfd, exec_path, target_argv, target_environ, regs,
         info, &bprm);
+    /* We shouldn't close at_execfd, it may be used later. */
+    if (execfd != at_execfd) {
+        close(execfd);
+    }
     if (ret != 0) {
         printf("Error while loading %s: %s\n", exec_path, strerror(-ret));
         _exit(EXIT_FAILURE);
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 945fc25279..3d8c57522d 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7613,8 +7613,11 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
     };
 
     if (is_proc_myself(pathname, "exe")) {
-        int execfd = qemu_getauxval(AT_EXECFD);
-        return execfd ? execfd : safe_openat(dirfd, exec_path, flags, mode);
+        /*
+         * We can't use AT_EXECFD here.
+         * User can close provided fd and another user will receive closed fd.
+         */
+        return safe_openat(dirfd, exec_path, flags, mode);
     }
 
     for (fake_open = fakes; fake_open->filename; fake_open++) {
diff --git a/tests/tcg/multiarch/linux-test.c b/tests/tcg/multiarch/linux-test.c
index 8a7c15cd31..bd370d973e 100644
--- a/tests/tcg/multiarch/linux-test.c
+++ b/tests/tcg/multiarch/linux-test.c
@@ -517,6 +517,89 @@ static void test_shm(void)
     chk_error(shmdt(ptr));
 }
 
+static void test_proc_myself_file(void)
+{
+    int fd1, fd2;
+    char link1[PATH_MAX], link2[PATH_MAX];
+    char buf1[PATH_MAX], buf2[PATH_MAX];
+    int buf1_length, buf2_length;
+
+    /* We can open any file that will always exist. */
+    const char *file_path = "/proc/self/comm";
+
+    char file_realpath[PATH_MAX];
+    if (realpath(file_path, file_realpath) == NULL) {
+        error("proc myself: invalid file");
+    }
+
+    fd1 = chk_error(open(file_path, O_RDONLY));
+    sprintf(link1, "/proc/self/fd/%d", fd1);
+
+    /* Lets try to open same file by first link. */
+    fd2 = chk_error(open(link1, O_RDONLY));
+    sprintf(link2, "/proc/self/fd/%d", fd2);
+
+    /* Two links should point to the same file path. */
+    buf1_length = chk_error(readlink(link1, buf1, PATH_MAX));
+    if (strlen(file_realpath) != buf1_length ||
+        strncmp(file_realpath, buf1, buf1_length) != 0) {
+        error("proc myself: invalid link");
+    }
+    buf2_length = chk_error(readlink(link2, buf2, PATH_MAX));
+    if (strlen(file_realpath) != buf2_length ||
+        strncmp(file_realpath, buf2, buf2_length) != 0) {
+        error("proc myself: invalid link");
+    }
+
+    /* We should be able to read same data from each fd. */
+    buf1_length = chk_error(read(fd1, buf1, PATH_MAX));
+    buf2_length = chk_error(read(fd2, buf2, PATH_MAX));
+    if (buf1_length == 0 || buf1_length != buf2_length ||
+        strncmp(buf1, buf2, buf2_length) != 0) {
+        error("proc myself: invalid file content");
+    }
+
+    chk_error(close(fd2));
+    chk_error(close(fd1));
+}
+
+static void test_proc_myself_exe(void)
+{
+    int fd1, fd2;
+    char link1[PATH_MAX], link2[PATH_MAX];
+    char buf1[PATH_MAX], buf2[PATH_MAX];
+    int buf1_length, buf2_length;
+
+    const char *exe_path = "/proc/self/exe";
+
+    char exe_realpath[PATH_MAX];
+    if (realpath(exe_path, exe_realpath) == NULL) {
+        error("proc myself: invalid exe");
+    }
+
+    fd1 = chk_error(open(exe_path, O_RDONLY));
+    sprintf(link1, "/proc/self/fd/%d", fd1);
+
+    /* Lets try to open link once again. */
+    fd2 = chk_error(open(link1, O_RDONLY));
+    sprintf(link2, "/proc/self/fd/%d", fd2);
+
+    /* Two links should point to the same exe path. */
+    buf1_length = chk_error(readlink(link1, buf1, PATH_MAX));
+    if (strlen(exe_realpath) != buf1_length ||
+        strncmp(exe_realpath, buf1, buf1_length) != 0) {
+        error("proc myself: invalid link");
+    }
+    buf2_length = chk_error(readlink(link2, buf2, PATH_MAX));
+    if (strlen(exe_realpath) != buf2_length ||
+        strncmp(exe_realpath, buf2, buf2_length) != 0) {
+        error("proc myself: invalid link");
+    }
+
+    chk_error(close(fd2));
+    chk_error(close(fd1));
+}
+
 int main(int argc, char **argv)
 {
     test_file();
@@ -532,5 +615,7 @@ int main(int argc, char **argv)
 
     test_signal();
     test_shm();
+    test_proc_myself_file();
+    test_proc_myself_exe();
     return 0;
 }
-- 
2.26.2

[PATCH 2/2] linux user: refactored is proc functions for syscalls

[Andrew Aladjev]

Signed-off-by: Andrew Aladjev <aladjev.andrew@gmail.com>
---
 linux-user/syscall.c | 81 ++++++++++++++++++++++++++++++--------------
 1 file changed, 56 insertions(+), 25 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 3d8c57522d..7b4d7cc197 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7482,38 +7482,69 @@ static int open_self_auxv(void *cpu_env, int fd)
     return 0;
 }
 
-static int is_proc_myself(const char *filename, const char *entry)
-{
-    if (!strncmp(filename, "/proc/", strlen("/proc/"))) {
-        filename += strlen("/proc/");
-        if (!strncmp(filename, "self/", strlen("self/"))) {
-            filename += strlen("self/");
-        } else if (*filename >= '1' && *filename <= '9') {
-            char myself[80];
-            snprintf(myself, sizeof(myself), "%d/", getpid());
-            if (!strncmp(filename, myself, strlen(myself))) {
-                filename += strlen(myself);
-            } else {
-                return 0;
-            }
-        } else {
-            return 0;
-        }
-        if (!strcmp(filename, entry)) {
-            return 1;
+#define PROC "/proc/"
+#define SELF "self/"
+
+#define STARTS_WITH(path, CONSTANT) (              \
+    strlen(path) >= strlen(CONSTANT) &&            \
+    strncmp(path, CONSTANT, strlen(CONSTANT)) == 0 \
+)
+
+static inline char *scope_to_proc(const char *path)
+{
+    if (STARTS_WITH(path, PROC)) {
+        return (char *)path + strlen(PROC);
+    }
+
+    return NULL;
+}
+
+static inline char *scope_to_proc_myself(const char *path)
+{
+    char *scope_path = scope_to_proc(path);
+    if (scope_path == NULL) {
+        return NULL;
+    }
+
+    if (STARTS_WITH(scope_path, SELF)) {
+        return scope_path + strlen(SELF);
+    }
+
+    if (strlen(scope_path) >= 1 &&
+        *scope_path >= '1' && *scope_path <= '9') {
+        char pid_path[80];
+        snprintf(pid_path, sizeof(pid_path), "%d/", getpid());
+        if (STARTS_WITH(scope_path, pid_path)) {
+            return scope_path + strlen(pid_path);
         }
     }
-    return 0;
+
+    return NULL;
 }
 
 #if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN) || \
     defined(TARGET_SPARC) || defined(TARGET_M68K) || defined(TARGET_HPPA)
-static int is_proc(const char *filename, const char *entry)
+static int is_proc(const char *path, const char *entry)
 {
-    return strcmp(filename, entry) == 0;
+    char *scope_path = scope_to_proc(path);
+    if (scope_path == NULL) {
+        return 0;
+    }
+
+    return strcmp(scope_path, entry) == 0;
 }
 #endif
 
+static int is_proc_myself(const char *path, const char *entry)
+{
+    char *scope_path = scope_to_proc_myself(path);
+    if (scope_path == NULL) {
+        return 0;
+    }
+
+    return strcmp(scope_path, entry) == 0;
+}
+
 #if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
 static int open_net_route(void *cpu_env, int fd)
 {
@@ -7601,13 +7632,13 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
         { "auxv", open_self_auxv, is_proc_myself },
         { "cmdline", open_self_cmdline, is_proc_myself },
 #if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
-        { "/proc/net/route", open_net_route, is_proc },
+        { "net/route", open_net_route, is_proc },
 #endif
 #if defined(TARGET_SPARC) || defined(TARGET_HPPA)
-        { "/proc/cpuinfo", open_cpuinfo, is_proc },
+        { "cpuinfo", open_cpuinfo, is_proc },
 #endif
 #if defined(TARGET_M68K)
-        { "/proc/hardware", open_hardware, is_proc },
+        { "hardware", open_hardware, is_proc },
 #endif
         { NULL, NULL, NULL }
     };
-- 
2.26.2