[PATCH 4.9 039/125] powerpc/64: Fix atomic64_inc_not_zero() to return an int

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.9 039/125] powerpc/64: Fix atomic64_inc_not_zero() to return an int
Date	2017-07-25 22:40 +0200
Message-ID	<u7eMA-7zW-67@gated-at.bofh.it> (permalink)
References	<u7dGN-6Sz-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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

------------------

From: Michael Ellerman <mpe@ellerman.id.au>

commit 01e6a61aceb82e13bec29502a8eb70d9574f97ad upstream.

Although it's not documented anywhere, there is an expectation that
atomic64_inc_not_zero() returns a result which fits in an int. This is
the behaviour implemented on all arches except powerpc.

This has caused at least one bug in practice, in the percpu-refcount
code, where the long result from our atomic64_inc_not_zero() was
truncated to an int leading to lost references and stuck systems. That
was worked around in that code in commit 966d2b04e070 ("percpu-refcount:
fix reference leak during percpu-atomic transition").

To the best of my grepping abilities there are no other callers
in-tree which truncate the value, but we should fix it anyway. Because
the breakage is subtle and potentially very harmful I'm also tagging
it for stable.

Code generation is largely unaffected because in most cases the
callers are just using the result for a test anyway. In particular the
case of fget() that was mentioned in commit a6cf7ed5119f
("powerpc/atomic: Implement atomic*_inc_not_zero") generates exactly
the same code.

Fixes: a6cf7ed5119f ("powerpc/atomic: Implement atomic*_inc_not_zero")
Noticed-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/include/asm/atomic.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/include/asm/atomic.h
+++ b/arch/powerpc/include/asm/atomic.h
@@ -560,7 +560,7 @@ static __inline__ int atomic64_add_unles
  * Atomically increments @v by 1, so long as @v is non-zero.
  * Returns non-zero if @v was non-zero, and zero otherwise.
  */
-static __inline__ long atomic64_inc_not_zero(atomic64_t *v)
+static __inline__ int atomic64_inc_not_zero(atomic64_t *v)
 {
 	long t1, t2;
 
@@ -579,7 +579,7 @@ static __inline__ long atomic64_inc_not_
 	: "r" (&v->counter)
 	: "cc", "xer", "memory");
 
-	return t1;
+	return t1 != 0;
 }
 
 #endif /* __powerpc64__ */

Thread

[PATCH 4.9 000/125] 4.9.40-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 068/125] ipmi: use rcu lock around call to intf->handlers->sender() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 046/125] PCI: rockchip: Use normal register bank for config accessors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 042/125] powerpc/asm: Mark cr0 as clobbered in mftb() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 035/125] scsi: Add STARGET_CREATED_REMOVE state to scsi_target_state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 044/125] af_key: Fix sadb_x_ipsecrequest parsing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 037/125] xen/scsiback: Fix a TMR related use-after-free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 053/125] usb: storage: return on error to avoid a null pointer dereference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 030/125] ASoC: compress: Derive substream from stream based on direction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 008/125] ath9k: fix tx99 bus error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 027/125] wlcore: fix 64K page support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 056/125] usb: renesas_usbhs: gadget: disable all eps when the driver stops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 047/125] PCI/PM: Restore the status of PCI devices across hibernation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 049/125] xhci: fix 20000ms port resume timeout Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 028/125] btrfs: Dont clear SGID when inheriting ACLs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 033/125] PM / Domains: Fix unsafe iteration over modified list of domains Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 052/125] [media] mxl111sf: Fix driver to use heap allocate buffers for USB messages Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 009/125] ath9k: fix an invalid pointer dereference in ath9k_rng_stop() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 041/125] powerpc: Fix emulation of mfocrf in emulate_step() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 043/125] powerpc/mm/radix: Properly clear process table entry Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 039/125] powerpc/64: Fix atomic64_inc_not_zero() to return an int Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 034/125] scsi: ses: do not add a device to an enclosure if enclosure_add_links() fails. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 029/125] igb: Explicitly select page 0 at initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 032/125] PM / Domains: Fix unsafe iteration over modified list of domain providers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 036/125] iscsi-target: Add login_keys_workaround attribute for non RFC initiators Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 054/125] USB: cdc-acm: add device-id for quirky printer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 071/125] f2fs: sanity check size of nat and sit cache Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 050/125] xhci: Fix NULL pointer dereference when cleaning up streams for removed host Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 069/125] ipmi:ssif: Add missing unlock in error branch Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 026/125] Bluetooth: use constant time memory comparison for secret values Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 031/125] PM / Domains: Fix unsafe iteration over modified list of device links Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 040/125] powerpc: Fix emulation of mcrf in emulate_step() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:40 +0200
  [PATCH 4.9 023/125] perf intel-pt: Ensure never to set last_ip when packet count is zero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 003/125] dm mpath: cleanup -Wbool-operation warning in choose_pgpath() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 017/125] NFC: Add sockaddr length checks before accessing sa_family in bind handlers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 018/125] perf intel-pt: Move decoder error setting into one condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 005/125] thermal: max77620: fix device-node reference imbalance Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 006/125] thermal: cpu_cooling: Avoid accessing potentially freed structures Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 004/125] [media] s5p-jpeg: dont return a random width/height Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 001/125] disable new gcc-7.1.1 warnings for now Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 015/125] nfc: Ensure presence of required attributes in the activate_target handler Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 020/125] perf intel-pt: Fix missing stack clear Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 002/125] [media] ir-core: fix gcc-7 warning on bool arithmetic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 012/125] NFC: nfcmrvl: do not use device-managed resources Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 007/125] ath9k: fix tx99 use after free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 021/125] perf intel-pt: Ensure IP is zero when state is INTEL_PT_STATE_NO_IP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 011/125] NFC: nfcmrvl_uart: add missing tty-device sanity check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 014/125] NFC: nfcmrvl: fix firmware-management initialisation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 016/125] nfc: Fix the sockaddr length sanitization in llcp_sock_connect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 019/125] perf intel-pt: Improve sample timestamp Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 010/125] NFC: fix broken device allocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  [PATCH 4.9 013/125] NFC: nfcmrvl: use nfc-device for firmware download Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 22:50 +0200
  Re: [PATCH 4.9 000/125] 4.9.40-stable review Guenter Roeck <linux@roeck-us.net> - 2017-07-26 05:00 +0200
  Re: [PATCH 4.9 000/125] 4.9.40-stable review Sumit Semwal <sumit.semwal@linaro.org> - 2017-07-26 16:20 +0200
    Re: [PATCH 4.9 000/125] 4.9.40-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-26 22:00 +0200
  Re: [PATCH 4.9 000/125] 4.9.40-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-07-26 16:30 +0200

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