Messages in this thread Patch in this message | | | Date | Sun, 19 Aug 2012 19:09:37 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 0/1] uprobes: mmap_region() corrupts mm->mm_rb if uprobe_mmap() fails |
| |
https://bugzilla.redhat.com/show_bug.cgi?id=843640
If mmap_region()->uprobe_mmap() fails, unmap_and_free_vma path does unmap_region() but does not remove the soon-to-be-freed vma from rb tree. Actually there are more problems but this is how William noticed this bug.
Perhaps we could do do_munmap() + return in this case, but in fact it is simply wrong to abort if uprobe_mmap() fails. Until at least we move the !UPROBE_COPY_INSN code from install_breakpoint() to uprobe_register().
For example, uprobe_mmap()->install_breakpoint() can fail if the probed insn is not supported (remember, uprobe_register() succeeds if nobody mmaps inode/offset), mmap() should not fail in this case.
dup_mmap()->uprobe_mmap() is wrong too by the same reason, fork() can race with uprobe_register() and fail for no reason if it wins the race and does install_breakpoint() first.
And, if nothing else, both mmap_region() and dup_mmap() return success if uprobe_mmap() fails. Change them to ignore the error code from uprobe_mmap().
Reported-and-tested-by: William Cohen <wcohen@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: <stable@vger.kernel.org> # v3.5 --- kernel/fork.c | 4 ++-- mm/mmap.c | 5 ++--- 2 files changed, 4 insertions(+), 5 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c index ab5211b..54bb88a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -454,8 +454,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) if (retval) goto out; - if (file && uprobe_mmap(tmp)) - goto out; + if (file) + uprobe_mmap(tmp); } /* a new mm has just been created */ arch_dup_mmap(oldmm, mm); diff --git a/mm/mmap.c b/mm/mmap.c index 4fe2697..f25fd3f 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1355,9 +1355,8 @@ out: } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK)) make_pages_present(addr, addr + len); - if (file && uprobe_mmap(vma)) - /* matching probes but cannot insert */ - goto unmap_and_free_vma; + if (file) + uprobe_mmap(vma); return addr; -- 1.5.5.1
| |