diff options
author | Dan Carpenter <dan.carpenter@oracle.com> | 2017-08-18 06:30:30 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2017-08-29 05:55:15 -0400 |
commit | eaa2f87c6b840b83827c40db6eb8481689570259 (patch) | |
tree | 93449daec7e592149122d621150d06cb79ef6baf | |
parent | 9c3a815f471a84811cf8021cf64aae3b8081dfde (diff) |
x86/ldt: Fix off by one in get_segment_base()
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 <dan.carpenter@oracle.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-janitors@vger.kernel.org
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 <mingo@kernel.org>
-rw-r--r-- | arch/x86/events/core.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index af12e294caed..939050169d12 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c | |||
@@ -2335,12 +2335,9 @@ static unsigned long get_segment_base(unsigned int segment) | |||
2335 | #ifdef CONFIG_MODIFY_LDT_SYSCALL | 2335 | #ifdef CONFIG_MODIFY_LDT_SYSCALL |
2336 | struct ldt_struct *ldt; | 2336 | struct ldt_struct *ldt; |
2337 | 2337 | ||
2338 | if (idx > LDT_ENTRIES) | ||
2339 | return 0; | ||
2340 | |||
2341 | /* IRQs are off, so this synchronizes with smp_store_release */ | 2338 | /* IRQs are off, so this synchronizes with smp_store_release */ |
2342 | ldt = lockless_dereference(current->active_mm->context.ldt); | 2339 | ldt = lockless_dereference(current->active_mm->context.ldt); |
2343 | if (!ldt || idx > ldt->nr_entries) | 2340 | if (!ldt || idx >= ldt->nr_entries) |
2344 | return 0; | 2341 | return 0; |
2345 | 2342 | ||
2346 | desc = &ldt->entries[idx]; | 2343 | desc = &ldt->entries[idx]; |
@@ -2348,7 +2345,7 @@ static unsigned long get_segment_base(unsigned int segment) | |||
2348 | return 0; | 2345 | return 0; |
2349 | #endif | 2346 | #endif |
2350 | } else { | 2347 | } else { |
2351 | if (idx > GDT_ENTRIES) | 2348 | if (idx >= GDT_ENTRIES) |
2352 | return 0; | 2349 | return 0; |
2353 | 2350 | ||
2354 | desc = raw_cpu_ptr(gdt_page.gdt) + idx; | 2351 | desc = raw_cpu_ptr(gdt_page.gdt) + idx; |