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[PATCH 3.12 1/5] dm: fix AB-BA deadlock in __dm_destroy()

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  [PATCH 3.12 1/5] dm: fix AB-BA deadlock in __dm_destroy() Jiri Slaby <jslaby@suse.cz> - 2016-10-20 10:50 +0200
    [PATCH 3.12 5/5] mm: remove gup_flags FOLL_WRITE games from __get_user_pages() Jiri Slaby <jslaby@suse.cz> - 2016-10-20 10:50 +0200
    [PATCH 3.12 4/5] x86/build: Build compressed x86 kernels as PIE Jiri Slaby <jslaby@suse.cz> - 2016-10-20 10:50 +0200
    [PATCH 3.12 2/5] ratelimit: fix bug in time interval by resetting right begin time Jiri Slaby <jslaby@suse.cz> - 2016-10-20 10:50 +0200
    [PATCH 3.12 3/5] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap() Jiri Slaby <jslaby@suse.cz> - 2016-10-20 10:50 +0200
    [PATCH 3.12 1/5] dm: fix AB-BA deadlock in __dm_destroy() Jiri Slaby <jslaby@suse.cz> - 2016-10-20 11:00 +0200

#1504641 — [PATCH 3.12 1/5] dm: fix AB-BA deadlock in __dm_destroy()

From: Junichi Nomura <j-nomura@ce.jp.nec.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 2a708cff93f1845b9239bc7d6310aef54e716c6a upstream.

__dm_destroy() takes io_barrier SRCU lock (dm_get_live_table) and
suspend_lock in reverse order.  Doing so can cause AB-BA deadlock:

  __dm_destroy                    dm_swap_table
  ---------------------------------------------------
                                  mutex_lock(suspend_lock)
  dm_get_live_table()
    srcu_read_lock(io_barrier)
                                  dm_sync_table()
                                    synchronize_srcu(io_barrier)
                                      .. waiting for dm_put_live_table()
  mutex_lock(suspend_lock)
    .. waiting for suspend_lock

Fix this by taking the locks in proper order.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Fixes: ab7c7bb6f4ab ("dm: hold suspend_lock while suspending device during device deletion")
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/md/dm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5a0b1742f794..de444d3ae293 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2444,14 +2444,14 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
 	 * do not race with internal suspend.
 	 */
 	mutex_lock(&md->suspend_lock);
+	map = dm_get_live_table(md, &srcu_idx);
 	if (!dm_suspended_md(md)) {
 		dm_table_presuspend_targets(map);
 		dm_table_postsuspend_targets(map);
 	}
-	mutex_unlock(&md->suspend_lock);
-
 	/* dm_put_live_table must be before msleep, otherwise deadlock is possible */
 	dm_put_live_table(md, srcu_idx);
+	mutex_unlock(&md->suspend_lock);
 
 	/*
 	 * Rare, but there may be I/O requests still going to complete,
-- 
2.10.1

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#1504643 — [PATCH 3.12 5/5] mm: remove gup_flags FOLL_WRITE games from __get_user_pages()

From: Linus Torvalds <torvalds@linux-foundation.org>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 19be0eaffa3ac7d8eb6784ad9bdbc7d67ed8e619 upstream.

This is an ancient bug that was actually attempted to be fixed once
(badly) by me eleven years ago in commit 4ceb5db9757a ("Fix
get_user_pages() race for write access") but that was then undone due to
problems on s390 by commit f33ea7f404e5 ("fix get_user_pages bug").

In the meantime, the s390 situation has long been fixed, and we can now
fix it by checking the pte_dirty() bit properly (and do it better).  The
s390 dirty bit was implemented in abf09bed3cce ("s390/mm: implement
software dirty bits") which made it into v3.9.  Earlier kernels will
have to look at the page state itself.

Also, the VM has become more scalable, and what used a purely
theoretical race back then has become easier to trigger.

To fix it, we introduce a new internal FOLL_COW flag to mark the "yes,
we already did a COW" rather than play racy games with FOLL_WRITE that
is very fundamental, and then use the pte dirty flag to validate that
the FOLL_COW flag is still valid.

Reported-and-tested-by: Phil "not Paul" Oester <kernel@linuxace.com>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 include/linux/mm.h |  1 +
 mm/memory.c        | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 79aa518c16a3..5676a670429e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1749,6 +1749,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
 #define FOLL_HWPOISON	0x100	/* check page is hwpoisoned */
 #define FOLL_NUMA	0x200	/* force NUMA hinting page fault */
 #define FOLL_MIGRATION	0x400	/* wait for page to replace migration entry */
+#define FOLL_COW	0x4000	/* internal GUP flag */
 
 typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
 			void *data);
diff --git a/mm/memory.c b/mm/memory.c
index 61926356c09a..a0c9c6cb59d1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1441,6 +1441,16 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 }
 EXPORT_SYMBOL_GPL(zap_vma_ptes);
 
+/*
+ * FOLL_FORCE can write to even unwritable pte's, but only
+ * after we've gone through a COW cycle and they are dirty.
+ */
+static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
+{
+	return pte_write(pte) ||
+		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
+}
+
 /**
  * follow_page_mask - look up a page descriptor from a user-virtual address
  * @vma: vm_area_struct mapping @address
@@ -1550,7 +1560,7 @@ split_fallthrough:
 	}
 	if ((flags & FOLL_NUMA) && pte_numa(pte))
 		goto no_page;
-	if ((flags & FOLL_WRITE) && !pte_write(pte))
+	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags))
 		goto unlock;
 
 	page = vm_normal_page(vma, address, pte);
@@ -1858,7 +1868,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 				 */
 				if ((ret & VM_FAULT_WRITE) &&
 				    !(vma->vm_flags & VM_WRITE))
-					foll_flags &= ~FOLL_WRITE;
+					foll_flags |= FOLL_COW;
 
 				cond_resched();
 			}
-- 
2.10.1

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#1504649 — [PATCH 3.12 4/5] x86/build: Build compressed x86 kernels as PIE

From: "H.J. Lu" <hjl.tools@gmail.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 6d92bc9d483aa1751755a66fee8fb39dffb088c0 upstream.

The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X
relocation to get the symbol address in PIC.  When the compressed x86
kernel isn't built as PIC, the linker optimizes R_386_GOT32X relocations
to their fixed symbol addresses.  However, when the compressed x86
kernel is loaded at a different address, it leads to the following
load failure:

  Failed to allocate space for phdrs

during the decompression stage.

If the compressed x86 kernel is relocatable at run-time, it should be
compiled with -fPIE, instead of -fPIC, if possible and should be built as
Position Independent Executable (PIE) so that linker won't optimize
R_386_GOT32X relocation to its fixed symbol address.

Older linkers generate R_386_32 relocations against locally defined
symbols, _bss, _ebss, _got and _egot, in PIE.  It isn't wrong, just less
optimal than R_386_RELATIVE.  But the x86 kernel fails to properly handle
R_386_32 relocations when relocating the kernel.  To generate
R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as
hidden in both 32-bit and 64-bit x86 kernels.

To build a 64-bit compressed x86 kernel as PIE, we need to disable the
relocation overflow check to avoid relocation overflow errors. We do
this with a new linker command-line option, -z noreloc-overflow, which
got added recently:

 commit 4c10bbaa0912742322f10d9d5bb630ba4e15dfa7
 Author: H.J. Lu <hjl.tools@gmail.com>
 Date:   Tue Mar 15 11:07:06 2016 -0700

    Add -z noreloc-overflow option to x86-64 ld

    Add -z noreloc-overflow command-line option to the x86-64 ELF linker to
    disable relocation overflow check.  This can be used to avoid relocation
    overflow check if there will be no dynamic relocation overflow at
    run-time.

The 64-bit compressed x86 kernel is built as PIE only if the linker supports
-z noreloc-overflow.  So far 64-bit relocatable compressed x86 kernel
boots fine even when it is built as a normal executable.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
[ Edited the changelog and comments. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 arch/x86/boot/compressed/Makefile  | 14 +++++++++++++-
 arch/x86/boot/compressed/head_32.S | 28 ++++++++++++++++++++++++++++
 arch/x86/boot/compressed/head_64.S |  8 ++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index c8a6792e7842..3980c0571d4a 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -8,7 +8,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
 	vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4
 
 KBUILD_CFLAGS := -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2
-KBUILD_CFLAGS += -fno-strict-aliasing -fPIC
+KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC)
 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
 cflags-$(CONFIG_X86_32) := -march=i386
 cflags-$(CONFIG_X86_64) := -mcmodel=small
@@ -21,6 +21,18 @@ KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
 
 LDFLAGS := -m elf_$(UTS_MACHINE)
+ifeq ($(CONFIG_RELOCATABLE),y)
+# If kernel is relocatable, build compressed kernel as PIE.
+ifeq ($(CONFIG_X86_32),y)
+LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
+else
+# To build 64-bit compressed kernel as PIE, we disable relocation
+# overflow check to avoid relocation overflow error with a new linker
+# command-line option, -z noreloc-overflow.
+LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
+	&& echo "-z noreloc-overflow -pie --no-dynamic-linker")
+endif
+endif
 LDFLAGS_vmlinux := -T
 
 hostprogs-y	:= mkpiggy
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 36ddc61182af..8e9fde129524 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -30,6 +30,34 @@
 #include <asm/boot.h>
 #include <asm/asm-offsets.h>
 
+/*
+ * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X
+ * relocation to get the symbol address in PIC.  When the compressed x86
+ * kernel isn't built as PIC, the linker optimizes R_386_GOT32X
+ * relocations to their fixed symbol addresses.  However, when the
+ * compressed x86 kernel is loaded at a different address, it leads
+ * to the following load failure:
+ *
+ *   Failed to allocate space for phdrs
+ *
+ * during the decompression stage.
+ *
+ * If the compressed x86 kernel is relocatable at run-time, it should be
+ * compiled with -fPIE, instead of -fPIC, if possible and should be built as
+ * Position Independent Executable (PIE) so that linker won't optimize
+ * R_386_GOT32X relocation to its fixed symbol address.  Older
+ * linkers generate R_386_32 relocations against locally defined symbols,
+ * _bss, _ebss, _got and _egot, in PIE.  It isn't wrong, just less
+ * optimal than R_386_RELATIVE.  But the x86 kernel fails to properly handle
+ * R_386_32 relocations when relocating the kernel.  To generate
+ * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as
+ * hidden:
+ */
+	.hidden _bss
+	.hidden _ebss
+	.hidden _got
+	.hidden _egot
+
 	__HEAD
 ENTRY(startup_32)
 #ifdef CONFIG_EFI_STUB
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index a55840367359..ce2925e55148 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -32,6 +32,14 @@
 #include <asm/processor-flags.h>
 #include <asm/asm-offsets.h>
 
+/*
+ * Locally defined symbols should be marked hidden:
+ */
+	.hidden _bss
+	.hidden _ebss
+	.hidden _got
+	.hidden _egot
+
 	__HEAD
 	.code32
 ENTRY(startup_32)
-- 
2.10.1

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#1504651 — [PATCH 3.12 2/5] ratelimit: fix bug in time interval by resetting right begin time

From: Jaewon Kim <jaewon31.kim@samsung.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit c2594bc37f4464bc74f2c119eb3269a643400aa0 upstream.

rs->begin in ratelimit is set in two cases.
 1) when rs->begin was not initialized
 2) when rs->interval was passed

For case #2, current ratelimit sets the begin to 0.  This incurrs
improper suppression.  The begin value will be set in the next ratelimit
call by 1).  Then the time interval check will be always false, and
rs->printed will not be initialized.  Although enough time passed,
ratelimit may return 0 if rs->printed is not less than rs->burst.  To
reset interval properly, begin should be jiffies rather than 0.

For an example code below:

    static DEFINE_RATELIMIT_STATE(mylimit, 1, 1);
    for (i = 1; i <= 10; i++) {
        if (__ratelimit(&mylimit))
            printk("ratelimit test count %d\n", i);
        msleep(3000);
    }

test result in the current code shows suppression even there is 3 seconds sleep.

  [  78.391148] ratelimit test count 1
  [  81.295988] ratelimit test count 2
  [  87.315981] ratelimit test count 4
  [  93.336267] ratelimit test count 6
  [  99.356031] ratelimit test count 8
  [ 105.376367] ratelimit test count 10

Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 lib/ratelimit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 40e03ea2a967..2c5de86460c5 100644
--- a/lib/ratelimit.c
+++ b/lib/ratelimit.c
@@ -49,7 +49,7 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 		if (rs->missed)
 			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
 				func, rs->missed);
-		rs->begin   = 0;
+		rs->begin   = jiffies;
 		rs->printed = 0;
 		rs->missed  = 0;
 	}
-- 
2.10.1

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#1504652 — [PATCH 3.12 3/5] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

From: Arend Van Spriel <arend.vanspriel@broadcom.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit ded89912156b1a47d940a0c954c43afbabd0c42c upstream.

User-space can choose to omit NL80211_ATTR_SSID and only provide raw
IE TLV data. When doing so it can provide SSID IE with length exceeding
the allowed size. The driver further processes this IE copying it
into a local variable without checking the length. Hence stack can be
corrupted and used as exploit.

Reported-by: Daxing Guo <freener.gdx@gmail.com>
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Acked-by: Benjamin Poirier <bpoirier@suse.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
index 571f013cebbb..f2e245bc4520 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
@@ -3731,7 +3731,7 @@ brcmf_cfg80211_start_ap(struct wiphy *wiphy, struct net_device *ndev,
 				(u8 *)&settings->beacon.head[ie_offset],
 				settings->beacon.head_len - ie_offset,
 				WLAN_EID_SSID);
-		if (!ssid_ie)
+		if (!ssid_ie || ssid_ie->len > IEEE80211_MAX_SSID_LEN)
 			return -EINVAL;
 
 		memcpy(ssid_le.SSID, ssid_ie->data, ssid_ie->len);
-- 
2.10.1

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#1504659

From: Junichi Nomura <j-nomura@ce.jp.nec.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 2a708cff93f1845b9239bc7d6310aef54e716c6a upstream.

__dm_destroy() takes io_barrier SRCU lock (dm_get_live_table) and
suspend_lock in reverse order.  Doing so can cause AB-BA deadlock:

  __dm_destroy                    dm_swap_table
  ---------------------------------------------------
                                  mutex_lock(suspend_lock)
  dm_get_live_table()
    srcu_read_lock(io_barrier)
                                  dm_sync_table()
                                    synchronize_srcu(io_barrier)
                                      .. waiting for dm_put_live_table()
  mutex_lock(suspend_lock)
    .. waiting for suspend_lock

Fix this by taking the locks in proper order.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Fixes: ab7c7bb6f4ab ("dm: hold suspend_lock while suspending device during device deletion")
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/md/dm.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5a0b1742f794..78ab0a131cf1 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2434,7 +2434,6 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
 	might_sleep();
 
 	spin_lock(&_minor_lock);
-	map = dm_get_live_table(md, &srcu_idx);
 	idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
 	set_bit(DMF_FREEING, &md->flags);
 	spin_unlock(&_minor_lock);
@@ -2444,14 +2443,14 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
 	 * do not race with internal suspend.
 	 */
 	mutex_lock(&md->suspend_lock);
+	map = dm_get_live_table(md, &srcu_idx);
 	if (!dm_suspended_md(md)) {
 		dm_table_presuspend_targets(map);
 		dm_table_postsuspend_targets(map);
 	}
-	mutex_unlock(&md->suspend_lock);
-
 	/* dm_put_live_table must be before msleep, otherwise deadlock is possible */
 	dm_put_live_table(md, srcu_idx);
+	mutex_unlock(&md->suspend_lock);
 
 	/*
 	 * Rare, but there may be I/O requests still going to complete,
-- 
2.10.1

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