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[PATCH 1/2] linux user: fixed proc myself execfd behaviour, added tests
From: |
Andrew Aladjev |
Subject: |
[PATCH 1/2] linux user: fixed proc myself execfd behaviour, added tests for proc myself fd |
Date: |
Thu, 20 Aug 2020 20:38:38 +0300 |
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 1/2] linux user: fixed proc myself execfd behaviour, added tests for proc myself fd,
Andrew Aladjev <=