diff options
| author | David Howells <dhowells@redhat.com> | 2006-09-27 01:50:19 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-27 08:26:14 -0700 |
| commit | d00c7b993712e4bb16d0012b35b654e40159b327 (patch) | |
| tree | 79f8fc60f8e41e054abc39b5d69e84d7a389777c | |
| parent | 7b4d5b8b39fd3701ed3693a89f2bd8f6ef49bce2 (diff) | |
[PATCH] NOMMU: Permit ptrace to ignore non-PROT_WRITE VMAs in NOMMU mode
Permit ptrace to modify a section that's non-shared but is marked
unwritable, such as is obtained by mapping the text segment of an ELF-FDPIC
executable binary with into a binary that's being ptraced[*].
[*] Under NOMMU conditions ptrace causes read-only MAP_PRIVATE mmaps to become
totally private copies because if a private mapping was actually shared
then the debugging setting breakpoints in it would potentially crash
other processes.
This is done by using the VM_MAYWRITE flag rather than the VM_WRITE flag
when deciding whether to permit a write.
Without this patch a debugger can't set breakpoints in the mapped text
sections of executables that are mapped read-only private, even if the
mmap() syscall has taken a private copy because PT_PTRACED is set.
In addition, VM_MAYREAD is used instead of VM_READ for similar reasons.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | mm/nommu.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/nommu.c b/mm/nommu.c index 2e140a6ae22..829fc904de1 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1258,9 +1258,9 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in len = vma->vm_end - addr; /* only read or write mappings where it is permitted */ - if (write && vma->vm_flags & VM_WRITE) + if (write && vma->vm_flags & VM_MAYWRITE) len -= copy_to_user((void *) addr, buf, len); - else if (!write && vma->vm_flags & VM_READ) + else if (!write && vma->vm_flags & VM_MAYREAD) len -= copy_from_user(buf, (void *) addr, len); else len = 0; |