Some of the page fault handlers do not deal with the following case
correctly:
* handle_mm_fault() has returned VM_FAULT_RETRY
* there is a pending fatal signal
* fault had happened in kernel mode
Correct action in such case is not "return unconditionally" - fatal
signals are handled only upon return to userland and something like
copy_to_user() would end up retrying the faulting instruction and
triggering the same fault again and again.
What we need to do in such case is to make the caller to treat that
as failed uaccess attempt - handle exception if there is an exception
handler for faulting instruction or oops if there isn't one.
Over the years some architectures had been fixed and now are handling
that case properly; some still do not. This series should fix the
remaining ones.
Status:
m68k, riscv, hexagon, parisc: tested/acked by maintainers.
alpha, sparc32, sparc64: tested locally - bug has been
reproduced on the unpatched kernel and verified to be fixed by
this series.
ia64, microblaze, nios2, openrisc: build, but otherwise
completely untested.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Merge tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull VM_FAULT_RETRY fixes from Al Viro:
"Some of the page fault handlers do not deal with the following case
correctly:
- handle_mm_fault() has returned VM_FAULT_RETRY
- there is a pending fatal signal
- fault had happened in kernel mode
Correct action in such case is not "return unconditionally" - fatal
signals are handled only upon return to userland and something like
copy_to_user() would end up retrying the faulting instruction and
triggering the same fault again and again.
What we need to do in such case is to make the caller to treat that as
failed uaccess attempt - handle exception if there is an exception
handler for faulting instruction or oops if there isn't one.
Over the years some architectures had been fixed and now are handling
that case properly; some still do not. This series should fix the
remaining ones.
Status:
- m68k, riscv, hexagon, parisc: tested/acked by maintainers.
- alpha, sparc32, sparc64: tested locally - bug has been reproduced
on the unpatched kernel and verified to be fixed by this series.
- ia64, microblaze, nios2, openrisc: build, but otherwise completely
untested"
* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
openrisc: fix livelock in uaccess
nios2: fix livelock in uaccess
microblaze: fix livelock in uaccess
ia64: fix livelock in uaccess
sparc: fix livelock in uaccess
alpha: fix livelock in uaccess
parisc: fix livelock in uaccess
hexagon: fix livelock in uaccess
riscv: fix livelock in uaccess
m68k: fix livelock in uaccess
1a8d05a726