diff options
authorDavid Howells <dhowells@redhat.com>2006-09-27 01:50:19 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-27 08:26:14 -0700
commitd00c7b993712e4bb16d0012b35b654e40159b327 (patch)
parent7b4d5b8b39fd3701ed3693a89f2bd8f6ef49bce2 (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>
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/nommu.c b/mm/nommu.c
index 2e140a6ae22e..829fc904de11 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);
len = 0;

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