| Message ID | 20230306135520.4222-1-ldufour@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | powerpc/mm: fix mmap_lock bad unlock | expand |
On 06.03.23 14:55, Laurent Dufour wrote: > When page fault is tried holding the per VMA lock, bad_access_pkey() and > bad_access() should not be called because it is assuming the mmap_lock is > held. > In the case a bad access is detected, fall back to the default path, > grabbing the mmap_lock to handle the fault and report the error. > > Fixes: 169db3bb4609 ("powerc/mm: try VMA lock-based page fault handling first") > Reported-by: Sachin Sant <sachinp@linux.ibm.com> > Link: https://lore.kernel.org/linux-mm/842502FB-F99C-417C-9648-A37D0ECDC9CE@linux.ibm.com > Cc: Suren Baghdasaryan <surenb@google.com> > Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> > --- > arch/powerpc/mm/fault.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index c7ae86b04b8a..e191b3ebd8d6 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -479,17 +479,13 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address, > > if (unlikely(access_pkey_error(is_write, is_exec, > (error_code & DSISR_KEYFAULT), vma))) { > - int rc = bad_access_pkey(regs, address, vma); > - > vma_end_read(vma); > - return rc; > + goto lock_mmap; > } > > if (unlikely(access_error(is_write, is_exec, vma))) { > - int rc = bad_access(regs, address); > - > vma_end_read(vma); > - return rc; > + goto lock_mmap; > } > > fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); IIUC, that commit is neither upstream not in mm-stable -- it's unstable. Maybe raise that as a review comment in reply to the original patch, so we can easily connect the dots and squash it into the original, problematic patch that is still under review.
On 06/03/2023 15:07:26, David Hildenbrand wrote: > On 06.03.23 14:55, Laurent Dufour wrote: >> When page fault is tried holding the per VMA lock, bad_access_pkey() and >> bad_access() should not be called because it is assuming the mmap_lock is >> held. >> In the case a bad access is detected, fall back to the default path, >> grabbing the mmap_lock to handle the fault and report the error. >> >> Fixes: 169db3bb4609 ("powerc/mm: try VMA lock-based page fault handling >> first") >> Reported-by: Sachin Sant <sachinp@linux.ibm.com> >> Link: >> https://lore.kernel.org/linux-mm/842502FB-F99C-417C-9648-A37D0ECDC9CE@linux.ibm.com >> Cc: Suren Baghdasaryan <surenb@google.com> >> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> >> --- >> arch/powerpc/mm/fault.c | 8 ++------ >> 1 file changed, 2 insertions(+), 6 deletions(-) >> >> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c >> index c7ae86b04b8a..e191b3ebd8d6 100644 >> --- a/arch/powerpc/mm/fault.c >> +++ b/arch/powerpc/mm/fault.c >> @@ -479,17 +479,13 @@ static int ___do_page_fault(struct pt_regs *regs, >> unsigned long address, >> if (unlikely(access_pkey_error(is_write, is_exec, >> (error_code & DSISR_KEYFAULT), vma))) { >> - int rc = bad_access_pkey(regs, address, vma); >> - >> vma_end_read(vma); >> - return rc; >> + goto lock_mmap; >> } >> if (unlikely(access_error(is_write, is_exec, vma))) { >> - int rc = bad_access(regs, address); >> - >> vma_end_read(vma); >> - return rc; >> + goto lock_mmap; >> } >> fault = handle_mm_fault(vma, address, flags | >> FAULT_FLAG_VMA_LOCK, regs); > > IIUC, that commit is neither upstream not in mm-stable -- it's unstable. > Maybe raise that as a review comment in reply to the original patch, so we > can easily connect the dots and squash it into the original, problematic > patch that is still under review. > Oh yes, I missed that. I'll reply to the Suren's thread. Thanks, Laurent.
On Mon, Mar 6, 2023 at 6:09 AM Laurent Dufour <ldufour@linux.ibm.com> wrote: > > On 06/03/2023 15:07:26, David Hildenbrand wrote: > > On 06.03.23 14:55, Laurent Dufour wrote: > >> When page fault is tried holding the per VMA lock, bad_access_pkey() and > >> bad_access() should not be called because it is assuming the mmap_lock is > >> held. > >> In the case a bad access is detected, fall back to the default path, > >> grabbing the mmap_lock to handle the fault and report the error. > >> > >> Fixes: 169db3bb4609 ("powerc/mm: try VMA lock-based page fault handling > >> first") > >> Reported-by: Sachin Sant <sachinp@linux.ibm.com> > >> Link: > >> https://lore.kernel.org/linux-mm/842502FB-F99C-417C-9648-A37D0ECDC9CE@linux.ibm.com > >> Cc: Suren Baghdasaryan <surenb@google.com> > >> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> > >> --- > >> arch/powerpc/mm/fault.c | 8 ++------ > >> 1 file changed, 2 insertions(+), 6 deletions(-) > >> > >> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > >> index c7ae86b04b8a..e191b3ebd8d6 100644 > >> --- a/arch/powerpc/mm/fault.c > >> +++ b/arch/powerpc/mm/fault.c > >> @@ -479,17 +479,13 @@ static int ___do_page_fault(struct pt_regs *regs, > >> unsigned long address, > >> if (unlikely(access_pkey_error(is_write, is_exec, > >> (error_code & DSISR_KEYFAULT), vma))) { > >> - int rc = bad_access_pkey(regs, address, vma); > >> - > >> vma_end_read(vma); > >> - return rc; > >> + goto lock_mmap; > >> } > >> if (unlikely(access_error(is_write, is_exec, vma))) { > >> - int rc = bad_access(regs, address); > >> - > >> vma_end_read(vma); > >> - return rc; > >> + goto lock_mmap; > >> } > >> fault = handle_mm_fault(vma, address, flags | > >> FAULT_FLAG_VMA_LOCK, regs); > > > > IIUC, that commit is neither upstream not in mm-stable -- it's unstable. > > Maybe raise that as a review comment in reply to the original patch, so we > > can easily connect the dots and squash it into the original, problematic > > patch that is still under review. > > > Oh yes, I missed that. I'll reply to the Suren's thread. Thanks Laurent! Seems simple enough to patch the original change. > > Thanks, > Laurent.
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index c7ae86b04b8a..e191b3ebd8d6 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -479,17 +479,13 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address, if (unlikely(access_pkey_error(is_write, is_exec, (error_code & DSISR_KEYFAULT), vma))) { - int rc = bad_access_pkey(regs, address, vma); - vma_end_read(vma); - return rc; + goto lock_mmap; } if (unlikely(access_error(is_write, is_exec, vma))) { - int rc = bad_access(regs, address); - vma_end_read(vma); - return rc; + goto lock_mmap; } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
When page fault is tried holding the per VMA lock, bad_access_pkey() and bad_access() should not be called because it is assuming the mmap_lock is held. In the case a bad access is detected, fall back to the default path, grabbing the mmap_lock to handle the fault and report the error. Fixes: 169db3bb4609 ("powerc/mm: try VMA lock-based page fault handling first") Reported-by: Sachin Sant <sachinp@linux.ibm.com> Link: https://lore.kernel.org/linux-mm/842502FB-F99C-417C-9648-A37D0ECDC9CE@linux.ibm.com Cc: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> --- arch/powerpc/mm/fault.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)