]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
powerpc/tm: Fix userspace stack corruption on signal delivery for active transactions
authorMichael Neuling <mikey@neuling.org>
Sun, 26 May 2013 18:09:41 +0000 (18:09 +0000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Fri, 31 May 2013 22:29:23 +0000 (08:29 +1000)
commit2b3f8e87cf99a33fb6faf5026d7147748bbd77b6
treedfeb4cb63821ec34279d26b0ac7a35d96316b648
parentb75c100ef24894bd2c8b52e123bcc5f191c5d9fd
powerpc/tm: Fix userspace stack corruption on signal delivery for active transactions

When in an active transaction that takes a signal, we need to be careful with
the stack.  It's possible that the stack has moved back up after the tbegin.
The obvious case here is when the tbegin is called inside a function that
returns before a tend.  In this case, the stack is part of the checkpointed
transactional memory state.  If we write over this non transactionally or in
suspend, we are in trouble because if we get a tm abort, the program counter
and stack pointer will be back at the tbegin but our in memory stack won't be
valid anymore.

To avoid this, when taking a signal in an active transaction, we need to use
the stack pointer from the checkpointed state, rather than the speculated
state.  This ensures that the signal context (written tm suspended) will be
written below the stack required for the rollback.  The transaction is aborted
becuase of the treclaim, so any memory written between the tbegin and the
signal will be rolled back anyway.

For signals taken in non-TM or suspended mode, we use the
normal/non-checkpointed stack pointer.

Tested with 64 and 32 bit signals

Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> # v3.9
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Documentation/powerpc/transactional_memory.txt
arch/powerpc/include/asm/processor.h
arch/powerpc/include/asm/signal.h
arch/powerpc/kernel/signal.c
arch/powerpc/kernel/signal.h
arch/powerpc/kernel/signal_32.c
arch/powerpc/kernel/signal_64.c