Patchwork linux-user: add support of binfmt_misc 'O' flag

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Submitter Laurent Vivier
Date Jan. 27, 2013, 2:03 a.m.
Message ID <1359252201-8647-1-git-send-email-laurent@vivier.eu>
Download mbox | patch
Permalink /patch/215941/
State New
Headers show

Comments

Laurent Vivier - Jan. 27, 2013, 2:03 a.m.
The binfmt_misc module can calculate the credentials and security
token according to the binary instead of to the interpreter if the
'C' flag is enabled.

To be able to execute non-readable binaries, this flag implies 'O'
flag. When 'O' flag is enabled, bintfmt_misc opens the file for
reading and pass the file descriptor to the interpreter.

References:
linux/Documentation/binfmt_misc.txt          ['O' and 'C' description]
linux/fs/binfmt_misc.c linux/fs/binfmt_elf.c [ AT_EXECFD usage ]

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/linuxload.c |    8 ++------
 linux-user/main.c      |   32 +++++++++++++++++++++++++++++++-
 linux-user/qemu.h      |    2 +-
 3 files changed, 34 insertions(+), 8 deletions(-)

Patch

diff --git a/linux-user/linuxload.c b/linux-user/linuxload.c
index 381ab89..2c3ec58 100644
--- a/linux-user/linuxload.c
+++ b/linux-user/linuxload.c
@@ -130,7 +130,7 @@  abi_ulong loader_build_argptr(int envc, int argc, abi_ulong sp,
     return sp;
 }
 
-int loader_exec(const char * filename, char ** argv, char ** envp,
+int loader_exec(int fdexec, const char *filename, char **argv, char **envp,
              struct target_pt_regs * regs, struct image_info *infop,
              struct linux_binprm *bprm)
 {
@@ -139,11 +139,7 @@  int loader_exec(const char * filename, char ** argv, char ** envp,
 
     bprm->p = TARGET_PAGE_SIZE*MAX_ARG_PAGES-sizeof(unsigned int);
     memset(bprm->page, 0, sizeof(bprm->page));
-    retval = open(filename, O_RDONLY);
-    if (retval < 0) {
-        return -errno;
-    }
-    bprm->fd = retval;
+    bprm->fd = fdexec;
     bprm->filename = (char *)filename;
     bprm->argc = count(argv);
     bprm->argv = argv;
diff --git a/linux-user/main.c b/linux-user/main.c
index fcbeaca..e2ed210 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -3385,6 +3385,26 @@  static int parse_args(int argc, char **argv)
     return optind;
 }
 
+static int get_execfd(char **envp)
+{
+    typedef struct {
+        long a_type;
+        long a_val;
+    } auxv_t;
+    auxv_t *auxv;
+
+    while (*envp++ != NULL) {
+        ;
+    }
+
+    for (auxv = (auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
+        if (auxv->a_type == AT_EXECFD) {
+            return auxv->a_val;
+        }
+    }
+    return -1;
+}
+
 int main(int argc, char **argv, char **envp)
 {
     const char *log_file = DEBUG_LOGFILE;
@@ -3399,6 +3419,7 @@  int main(int argc, char **argv, char **envp)
     int target_argc;
     int i;
     int ret;
+    int execfd;
 
     module_call_init(MODULE_INIT_QOM);
 
@@ -3543,7 +3564,16 @@  int main(int argc, char **argv, char **envp)
     env->opaque = ts;
     task_settid(ts);
 
-    ret = loader_exec(filename, target_argv, target_environ, regs,
+    execfd = get_execfd(envp);
+    if (execfd < 0) {
+        execfd = open(filename, O_RDONLY);
+    }
+    if (execfd < 0) {
+        printf("Error while loading %s: %s\n", filename, strerror(-execfd));
+        _exit(1);
+    }
+
+    ret = loader_exec(execfd, filename, target_argv, target_environ, regs,
         info, &bprm);
     if (ret != 0) {
         printf("Error while loading %s: %s\n", filename, strerror(-ret));
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index eb5ca6d..981ef2c 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -179,7 +179,7 @@  struct linux_binprm {
 void do_init_thread(struct target_pt_regs *regs, struct image_info *infop);
 abi_ulong loader_build_argptr(int envc, int argc, abi_ulong sp,
                               abi_ulong stringp, int push_ptr);
-int loader_exec(const char * filename, char ** argv, char ** envp,
+int loader_exec(int fdexec, const char *filename, char **argv, char **envp,
              struct target_pt_regs * regs, struct image_info *infop,
              struct linux_binprm *);