execve() fails to report errors

From: Pavel Machek (pavel@ucw.cz)
Date: Tue Mar 05 2002 - 18:34:37 EST

Hi!

Take this trivial .c program. Obviously correct.

struct foo {
        char fill[1*1024*1024*1024];
};

struct foo a;

void
main(void)
{
}

Compile. Run. Segfault.

Whose fault? Kernels; it fails to corectly report not enough address
space.

Now, I do not know if this is the right fix (binfmt_elf looks
spaghetty to me) but its certainly better than it was.

                                                        Pavel

--- clean/fs/binfmt_elf.c Tue Mar 5 21:52:44 2002
+++ linux/fs/binfmt_elf.c Wed Mar 6 00:14:31 2002
@@ -79,13 +79,19 @@
 
 #define BAD_ADDR(x) ((unsigned long)(x) > TASK_SIZE)
 
-static void set_brk(unsigned long start, unsigned long end)
+static int set_brk(unsigned long start, unsigned long end)
 {
+ int error;
         start = ELF_PAGEALIGN(start);
         end = ELF_PAGEALIGN(end);
         if (end <= start)
- return;
- do_brk(start, end - start);
+ return 0;
+
+ error = do_brk(start, end - start);
+ if (error!=start) {
+ return error;
+ }
+ return 0;
 }
 
 
@@ -606,7 +613,9 @@
                         /* There was a PT_LOAD segment with p_memsz > p_filesz
                            before this one. Map anonymous pages, if needed,
                            and clear the area. */
- set_brk (elf_bss + load_bias, elf_brk + load_bias);
+ retval = set_brk (elf_bss + load_bias, elf_brk + load_bias);
+ if (retval)
+ goto out_free_dentry;
                         nbyte = ELF_PAGEOFFSET(elf_bss);
                         if (nbyte) {
                                 nbyte = ELF_MIN_ALIGN - nbyte;
@@ -721,8 +730,7 @@
         /* Calling set_brk effectively mmaps the pages that we need
          * for the bss and break sections
          */
- set_brk(elf_bss, elf_brk);
-
+ retval = set_brk(elf_bss, elf_brk);
         padzero(elf_bss);
 
 #if 0
@@ -745,6 +753,7 @@
                 error = do_mmap(NULL, 0, 4096, PROT_READ | PROT_EXEC,
                                 MAP_FIXED | MAP_PRIVATE, 0);
                 up_write(&current->mm->mmap_sem);
+ /* FIXME: Check return from mmap! */
         }
 
 #ifdef ELF_PLAT_INIT
@@ -760,8 +769,7 @@
         start_thread(regs, elf_entry, bprm->p);
         if (current->ptrace & PT_PTRACED)
                 send_sig(SIGTRAP, current, 0);
- retval = 0;
 out:
         return retval;
 
         /* error cleanup */
@@ -842,9 +852,9 @@
 
         len = ELF_PAGESTART(elf_phdata->p_filesz + elf_phdata->p_vaddr + ELF_MIN_ALIGN - 1);
         bss = elf_phdata->p_memsz + elf_phdata->p_vaddr;
- if (bss > len)
- do_brk(len, bss - len);
         error = 0;
+ if (bss > len)
+ error = do_brk(len, bss - len);
 
 out_free_ph:
         kfree(elf_phdata); 

-- 
(about SSSCA) "I don't say this lightly.  However, I really think that the U.S.
no longer is classifiable as a democracy, but rather as a plutocracy." --hpa
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This archive was generated by hypermail 2b29 : Thu Mar 07 2002 - 21:00:54 EST