linux-kernel - [GIT pull] x86 fixes for 4.13

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Date:   Sun, 3 Sep 2017 11:06:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [GIT pull] x86 fixes for 4.13

Linus,

please pull the latest x86-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

This update contains:

 - Expand the space for uncompressing as the LZ4 worst case does not fit
   into the currently reserved space.

 - Validate boot parameters more strictly to prevent out of bound access in
   the decompressor/boot code.

 - Fix off by one errors in get_segment_base().

Thanks,

	tglx

------------------>
Dan Carpenter (1):
      x86/ldt: Fix off by one in get_segment_base()

Jan H. Schönherr (2):
      x86/boot: Provide more slack space during decompression
      x86/boot: Prevent faulty bootparams.screeninfo from causing harm


 arch/x86/boot/compressed/misc.c | 3 +--
 arch/x86/boot/header.S          | 8 +++++++-
 arch/x86/events/core.c          | 7 ++-----
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index a0838ab929f2..c14217cd0155 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -116,8 +116,7 @@ void __putstr(const char *s)
 		}
 	}
 
-	if (boot_params->screen_info.orig_video_mode == 0 &&
-	    lines == 0 && cols == 0)
+	if (lines == 0 || cols == 0)
 		return;
 
 	x = boot_params->screen_info.orig_x;
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 2ed8f0c25def..1bb08ecffd24 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -520,8 +520,14 @@ pref_address:		.quad LOAD_PHYSICAL_ADDR	# preferred load addr
 # the description in lib/decompressor_xxx.c for specific information.
 #
 # extra_bytes = (uncompressed_size >> 12) + 65536 + 128
+#
+# LZ4 is even worse: data that cannot be further compressed grows by 0.4%,
+# or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as
+# the size-dependent part now grows so fast.
+#
+# extra_bytes = (uncompressed_size >> 8) + 65536
 
-#define ZO_z_extra_bytes	((ZO_z_output_len >> 12) + 65536 + 128)
+#define ZO_z_extra_bytes	((ZO_z_output_len >> 8) + 65536)
 #if ZO_z_output_len > ZO_z_input_len
 # define ZO_z_extract_offset	(ZO_z_output_len + ZO_z_extra_bytes - \
 				 ZO_z_input_len)
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;