Commit-ID: eaa2f87c6b840b83827c40db6eb8481689570259
Gitweb: http://git.kernel.org/tip/eaa2f87c6b840b83827c40db6eb8481689570259
Author: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
AuthorDate: Fri, 18 Aug 2017 13:30:30 +0300
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 29 Aug 2017 11:55:15 +0200
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@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: kernel-janitors@xxxxxxxxxxxxxxx
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@xxxxxxxxxx>
---
arch/x86/events/core.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index af12e29..9390501 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;
--
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