diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2024-07-31 19:31:05 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2024-08-01 15:52:56 +0300 |
| commit | 41e71dbb0e0a0fe214545fe64af031303a08524c (patch) | |
| tree | c7fad64dc99dee2339fbefaa2989dde5e4220637 | |
| parent | bf514327c324bc8af64f359b341cc9b189c096fd (diff) | |
| download | linux-41e71dbb0e0a0fe214545fe64af031303a08524c.tar.xz | |
x86/mm: Fix pti_clone_pgtable() alignment assumption
Guenter reported dodgy crashes on an i386-nosmp build using GCC-11
that had the form of endless traps until entry stack exhaust and then
#DF from the stack guard.
It turned out that pti_clone_pgtable() had alignment assumptions on
the start address, notably it hard assumes start is PMD aligned. This
is true on x86_64, but very much not true on i386.
These assumptions can cause the end condition to malfunction, leading
to a 'short' clone. Guess what happens when the user mapping has a
short copy of the entry text?
Use the correct increment form for addr to avoid alignment
assumptions.
Fixes: 16a3fe634f6a ("x86/mm/pti: Clone kernel-image on PTE level for 32 bit")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20240731163105.GG33588@noisy.programming.kicks-ass.net
| -rw-r--r-- | arch/x86/mm/pti.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 2e69abf4f852..48c503208c79 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -374,14 +374,14 @@ pti_clone_pgtable(unsigned long start, unsigned long end, */ *target_pmd = *pmd; - addr += PMD_SIZE; + addr = round_up(addr + 1, PMD_SIZE); } else if (level == PTI_CLONE_PTE) { /* Walk the page-table down to the pte level */ pte = pte_offset_kernel(pmd, addr); if (pte_none(*pte)) { - addr += PAGE_SIZE; + addr = round_up(addr + 1, PAGE_SIZE); continue; } @@ -401,7 +401,7 @@ pti_clone_pgtable(unsigned long start, unsigned long end, /* Clone the PTE */ *target_pte = *pte; - addr += PAGE_SIZE; + addr = round_up(addr + 1, PAGE_SIZE); } else { BUG(); |