Commit 690dbe1c authored Aug 01, 2005 by Hugh Dickins Committed by Linus Torvalds Aug 01, 2005

[PATCH] x86_64: access of some bad address



x86_64 has a large sparse gate area between VSYSCALL_START and
VSYSCALL_END, not all of it presently backed by pmds.  Alexander Nyberg has
found that in some circumstances gdb may try to ptrace here, and hit
get_user_pages BUG_ON.  It seems odd that gdb should be accessing here, but
it certainly shouldn't crash in this way: relax BUG_ON to -EFAULT.  Fixes
kernel bugzilla #4801.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 74f9c9c2

mm/memory.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -910,9 +910,13 @@ int get_user_pages(struct task_struct tsk, struct mm_struct mm,
		pud = pud_offset(pgd, pg);
		BUG_ON(pud_none(*pud));
		pmd = pmd_offset(pud, pg);
		BUG_ON(pmd_none(*pmd));
		if (pmd_none(*pmd))
		return i ? : -EFAULT;
		pte = pte_offset_map(pmd, pg);
		BUG_ON(pte_none(*pte));
		if (pte_none(*pte)) {
		pte_unmap(pte);
		return i ? : -EFAULT;
		}
		if (pages) {
		pages[i] = pte_page(*pte);
		get_page(pages[i]);

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