3.16.50-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Dan Carpenter <[email protected]> commit eaa2f87c6b840b83827c40db6eb8481689570259 upstream. ldt->entries[] is allocated in alloc_ldt_struct(). It has ldt->nr_entries elements and ldt->nr_entries is capped at LDT_ENTRIES. So if "idx" is == ldt->nr_entries then we're reading beyond the end of the buffer. It seems duplicative to have two limit checks when one would work just as well so I removed the check against LDT_ENTRIES. The gdt_page.gdt[] array has GDT_ENTRIES entries. Signed-off-by: Dan Carpenter <[email protected]> Acked-by: Andy Lutomirski <[email protected]> Cc: Alexander Shishkin <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Fixes: d07bdfd322d3 ("perf/x86: Fix USER/KERNEL tagging of samples properly") Link: http://lkml.kernel.org/r/20170818102516.gqwm4xdvvuvjw5ho@mwanda Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.16: adjust filename, context] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/kernel/cpu/perf_event.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -2009,17 +2009,14 @@ static unsigned long get_segment_base(un if ((segment & SEGMENT_TI_MASK) == SEGMENT_LDT) { struct ldt_struct *ldt; - if (idx > LDT_ENTRIES) - return 0; - /* IRQs are off, so this synchronizes with smp_store_release */ ldt = lockless_dereference(current->active_mm->context.ldt); - if (!ldt || idx > ldt->size) + if (!ldt || idx >= ldt->size) return 0; desc = &ldt->entries[idx]; } else { - if (idx > GDT_ENTRIES) + if (idx >= GDT_ENTRIES) return 0; desc = __this_cpu_ptr(&gdt_page.gdt[0]) + idx;
