Commit df1e2fb5 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

[PATCH] shmdt: check address alignment

SUSv3 says the shmdt() function shall fail with EINVAL if the value of
shmaddr is not the data segment start address of a shared memory segment:
our sys_shmdt needs to reject a shmaddr which is not page-aligned.

Does it have the potential to break existing apps?

Hugh says

  "sys_shmdt() just does the wrong (unexpected) thing with a misaligned
  address: it'll fail on what you might expect it to succeed on, and only
  succeed on what it should definitely fail on.

  "That is, I think it behaves as if shmaddr gets rounded up, when the only
  understandable behaviour would be if it rounded it down.

  "Which does mean you'd have to be devious to see anything but EINVAL from
  a misaligned shmaddr there, so it's not terribly important."
Signed-off-by: default avatarHugh Dickins <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 38885bd4
......@@ -814,6 +814,9 @@ asmlinkage long sys_shmdt(char __user *shmaddr)
loff_t size = 0;
int retval = -EINVAL;
if (addr & ~PAGE_MASK)
return retval;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment