diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-28 09:13:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-28 09:13:08 -0700 |
| commit | 3f777e19d171670ab558a6d5e6b1ac7f9b6c574f (patch) | |
| tree | 2fa61424cd8288aa8711b1ed742eb27926a0501e /arch | |
| parent | 51184ae37e0518fd90cb437a2fbc953ae558cd0d (diff) | |
| parent | 316ec154810960052d4586b634156c54d0778f74 (diff) | |
Merge tag 'cve-2020-11884' from emailed bundle
Pull s390 fix from Christian Borntraeger:
"Fix a race between page table upgrade and uaccess on s390.
This fixes CVE-2020-11884 which allows for a local kernel crash or
code execution"
* tag 'cve-2020-11884' from emailed bundle:
s390/mm: fix page table upgrade vs 2ndary address mode accesses
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/lib/uaccess.c | 4 | ||||
| -rw-r--r-- | arch/s390/mm/pgalloc.c | 16 |
2 files changed, 18 insertions, 2 deletions
diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c index c4f8039a35e8..0267405ab7c6 100644 --- a/arch/s390/lib/uaccess.c +++ b/arch/s390/lib/uaccess.c @@ -64,10 +64,13 @@ mm_segment_t enable_sacf_uaccess(void) { mm_segment_t old_fs; unsigned long asce, cr; + unsigned long flags; old_fs = current->thread.mm_segment; if (old_fs & 1) return old_fs; + /* protect against a concurrent page table upgrade */ + local_irq_save(flags); current->thread.mm_segment |= 1; asce = S390_lowcore.kernel_asce; if (likely(old_fs == USER_DS)) { @@ -83,6 +86,7 @@ mm_segment_t enable_sacf_uaccess(void) __ctl_load(asce, 7, 7); set_cpu_flag(CIF_ASCE_SECONDARY); } + local_irq_restore(flags); return old_fs; } EXPORT_SYMBOL(enable_sacf_uaccess); diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c index 498c98a312f4..fff169d64711 100644 --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -70,8 +70,20 @@ static void __crst_table_upgrade(void *arg) { struct mm_struct *mm = arg; - if (current->active_mm == mm) - set_user_asce(mm); + /* we must change all active ASCEs to avoid the creation of new TLBs */ + if (current->active_mm == mm) { + S390_lowcore.user_asce = mm->context.asce; + if (current->thread.mm_segment == USER_DS) { + __ctl_load(S390_lowcore.user_asce, 1, 1); + /* Mark user-ASCE present in CR1 */ + clear_cpu_flag(CIF_ASCE_PRIMARY); + } + if (current->thread.mm_segment == USER_DS_SACF) { + __ctl_load(S390_lowcore.user_asce, 7, 7); + /* enable_sacf_uaccess does all or nothing */ + WARN_ON(!test_cpu_flag(CIF_ASCE_SECONDARY)); + } + } __tlb_flush_local(); } |