[GIT pull] x86 fixes for 4.13

From: Thomas Gleixner
Date: Sun Sep 03 2017 - 05:07:16 EST


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;