On Tue, 19 Jan 2021 11:38:10 +0100 Janosch Frank <[email protected]> wrote:
> On 1/19/21 11:25 AM, Christian Borntraeger wrote: > > > > > > On 19.01.21 11:04, Janosch Frank wrote: > >> Turns out that the bit 61 in the TEID is not always 1 and if that's > >> the case the address space ID and the address are > >> unpredictable. Without an address and it's address space ID we can't > >> export memory and hence we can only send a SIGSEGV to the process or > >> panic the kernel depending on who caused the exception. > >> > >> Signed-off-by: Janosch Frank <[email protected]> > >> Fixes: 084ea4d611a3d ("s390/mm: add (non)secure page access exceptions > >> handlers") > >> Cc: [email protected] > > > > Reviewed-by: Christian Borntraeger <[email protected]> > > Thanks! > > > > > some small things to consider (or to reject) > > > >> --- > >> arch/s390/mm/fault.c | 14 ++++++++++++++ > >> 1 file changed, 14 insertions(+) > >> > >> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > >> index e30c7c781172..5442937e5b4b 100644 > >> --- a/arch/s390/mm/fault.c > >> +++ b/arch/s390/mm/fault.c > >> @@ -791,6 +791,20 @@ void do_secure_storage_access(struct pt_regs *regs) > >> struct page *page; > >> int rc; > >> > >> + /* There are cases where we don't have a TEID. */ > >> + if (!(regs->int_parm_long & 0x4)) { > >> + /* > >> + * Userspace could for example try to execute secure > >> + * storage and trigger this. We should tell it that it > >> + * shouldn't do that. > > > > Maybe something like > > /* > > * when this happens, userspace did something that it s/when/When/ :) > > * was not supposed to do, e.g. branching into secure > > * secure memory. Trigger a segmentation fault. > >> + */ > > Sounds good > > >> + if (user_mode(regs)) { > >> + send_sig(SIGSEGV, current, 0); > >> + return; > >> + } else > >> + panic("Unexpected PGM 0x3d with TEID bit 61=0"); > > > > use BUG instead of panic? That would kill this process, but it allows > > people to maybe save unaffected data. > > That would make sense, will do With BUG(): Reviewed-by: Cornelia Huck <[email protected]>
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