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authorErnie Petrides <petrides@redhat.com>2006-08-26 10:20:45 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2006-09-08 14:51:39 -0700
commit4be6107d35a5b5f8eac9b92eef1e243a033a3f39 (patch)
parent2cd6b01ad38d34b805a0a052725ec3f37e387ecd (diff)
binfmt_elf: fix checks for bad address
Fix check for bad address; use macro instead of open-coding two checks. Taken from RHEL4 kernel update. For background, the BAD_ADDR() macro should return TRUE if the address is TASK_SIZE, because that's the lowest address that is *not* valid for user-space mappings. The macro was correct in binfmt_aout.c but was wrong for the "equal to" case in binfmt_elf.c. There were two in-line validations of user-space addresses in binfmt_elf.c, which have been appropriately converted to use the corrected BAD_ADDR() macro in the patch you posted yesterday. Note that the size checks against TASK_SIZE are okay as coded. The additional changes that I propose are below. These are in the error paths for bad ELF entry addresses once load_elf_binary() has already committed to exec'ing the new image (following the tearing down of the task's original address space). The 1st hunk deals with the interp-side of the outer "if". There were two problems here. The printk() should be removed because this path can be triggered at will by a bogus interpreter image created and used by a malicious user. Further, the error code should not be ENOEXEC, because that causes the loop in search_binary_handler() to continue trying other exec handlers (twice, in fact). But it's too late for this to work correctly, because the user address space has already been torn down, and an exec() failure cannot be returned to the user code because the code no longer exists. The only recovery is to force a SIGSEGV, but it's best to terminate the search loop immediately. I somewhat arbitrarily chose EINVAL as a fallback error code, but any error returned by load_elf_interp() will override that (but this value will never be seen by user-space). The 2nd hunk deals with the non-interp-side of the outer "if". There were two problems here as well. The SIGSEGV needs to be forced, because a prior sigaction() syscall might have set the associated disposition to SIG_IGN. And the ENOEXEC should be changed to EINVAL as described above. Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
1 files changed, 7 insertions, 8 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 537893a16014..997a20256dce 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -86,7 +86,7 @@ static struct linux_binfmt elf_format = {
.min_coredump = ELF_EXEC_PAGESIZE
-#define BAD_ADDR(x) ((unsigned long)(x) > TASK_SIZE)
+#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
static int set_brk(unsigned long start, unsigned long end)
@@ -389,7 +389,7 @@ static unsigned long load_elf_interp(struct elfhdr * interp_elf_ex,
* <= p_memsize so it is only necessary to check p_memsz.
k = load_addr + eppnt->p_vaddr;
- if (k > TASK_SIZE || eppnt->p_filesz > eppnt->p_memsz ||
+ if (BAD_ADDR(k) || eppnt->p_filesz > eppnt->p_memsz ||
eppnt->p_memsz > TASK_SIZE || TASK_SIZE - eppnt->p_memsz < k) {
error = -ENOMEM;
goto out_close;
@@ -876,7 +876,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
* allowed task size. Note that p_filesz must always be
* <= p_memsz so it is only necessary to check p_memsz.
- if (k > TASK_SIZE || elf_ppnt->p_filesz > elf_ppnt->p_memsz ||
+ if (BAD_ADDR(k) || elf_ppnt->p_filesz > elf_ppnt->p_memsz ||
elf_ppnt->p_memsz > TASK_SIZE ||
TASK_SIZE - elf_ppnt->p_memsz < k) {
/* set_brk can never work. Avoid overflows. */
@@ -930,10 +930,9 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
if (BAD_ADDR(elf_entry)) {
- printk(KERN_ERR "Unable to load interpreter %.128s\n",
- elf_interpreter);
force_sig(SIGSEGV, current);
- retval = -ENOEXEC; /* Nobody gets to see this, but.. */
+ retval = IS_ERR((void *)elf_entry) ?
+ (int)elf_entry : -EINVAL;
goto out_free_dentry;
reloc_func_desc = interp_load_addr;
@@ -944,8 +943,8 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
} else {
elf_entry = loc->elf_ex.e_entry;
if (BAD_ADDR(elf_entry)) {
- send_sig(SIGSEGV, current, 0);
- retval = -ENOEXEC; /* Nobody gets to see this, but.. */
+ force_sig(SIGSEGV, current);
+ retval = -EINVAL;
goto out_free_dentry;