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authorDan Carpenter <dan.carpenter@oracle.com>2017-08-18 13:30:30 +0300
committerIngo Molnar <mingo@kernel.org>2017-08-29 11:55:15 +0200
commiteaa2f87c6b840b83827c40db6eb8481689570259 (patch)
tree93449daec7e592149122d621150d06cb79ef6baf /arch/x86/events/core.c
parent9c3a815f471a84811cf8021cf64aae3b8081dfde (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>
Diffstat (limited to 'arch/x86/events/core.c')
-rw-r--r--arch/x86/events/core.c7
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)
#ifdef CONFIG_MODIFY_LDT_SYSCALL
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->nr_entries)
+ if (!ldt || idx >= ldt->nr_entries)
return 0;
desc = &ldt->entries[idx];
@@ -2348,7 +2345,7 @@ static unsigned long get_segment_base(unsigned int segment)
return 0;
#endif
} else {
- if (idx > GDT_ENTRIES)
+ if (idx >= GDT_ENTRIES)
return 0;
desc = raw_cpu_ptr(gdt_page.gdt) + idx;