kernel/linux.git/arch/powerpc/mm, branch linux-4.4.y

powerpc: Allow 4224 bytes of stack expansion for the signal frame

2020-08-26T08:27:09+00:00

commit 63dee5df43a31f3844efabc58972f0a206ca4534 upstream. We have powerpc specific logic in our page fault handling to decide if an access to an unmapped address below the stack pointer should expand the stack VMA. The code was originally added in 2004 "ported from 2.4". The rough logic is that the stack is allowed to grow to 1MB with no extra checking. Over 1MB the access must be within 2048 bytes of the stack pointer, or be from a user instruction that updates the stack pointer. The 2048 byte allowance below the stack pointer is there to cover the 288 byte "red zone" as well as the "about 1.5kB" needed by the signal delivery code. Unfortunately since then the signal frame has expanded, and is now 4224 bytes on 64-bit kernels with transactional memory enabled. This means if a process has consumed more than 1MB of stack, and its stack pointer lies less than 4224 bytes from the next page boundary, signal delivery will fault when trying to expand the stack and the process will see a SEGV. The total size of the signal frame is the size of struct rt_sigframe (which includes the red zone) plus __SIGNAL_FRAMESIZE (128 bytes on 64-bit). The 2048 byte allowance was correct until 2008 as the signal frame was: struct rt_sigframe { struct ucontext uc; /* 0 1440 */ /* --- cacheline 11 boundary (1408 bytes) was 32 bytes ago --- */ long unsigned int _unused[2]; /* 1440 16 */ unsigned int tramp[6]; /* 1456 24 */ struct siginfo * pinfo; /* 1480 8 */ void * puc; /* 1488 8 */ struct siginfo info; /* 1496 128 */ /* --- cacheline 12 boundary (1536 bytes) was 88 bytes ago --- */ char abigap[288]; /* 1624 288 */ /* size: 1920, cachelines: 15, members: 7 */ /* padding: 8 */ }; 1920 + 128 = 2048 Then in commit ce48b2100785 ("powerpc: Add VSX context save/restore, ptrace and signal support") (Jul 2008) the signal frame expanded to 2304 bytes: struct rt_sigframe { struct ucontext uc; /* 0 1696 */ <-- /* --- cacheline 13 boundary (1664 bytes) was 32 bytes ago --- */ long unsigned int _unused[2]; /* 1696 16 */ unsigned int tramp[6]; /* 1712 24 */ struct siginfo * pinfo; /* 1736 8 */ void * puc; /* 1744 8 */ struct siginfo info; /* 1752 128 */ /* --- cacheline 14 boundary (1792 bytes) was 88 bytes ago --- */ char abigap[288]; /* 1880 288 */ /* size: 2176, cachelines: 17, members: 7 */ /* padding: 8 */ }; 2176 + 128 = 2304 At this point we should have been exposed to the bug, though as far as I know it was never reported. I no longer have a system old enough to easily test on. Then in 2010 commit 320b2b8de126 ("mm: keep a guard page below a grow-down stack segment") caused our stack expansion code to never trigger, as there was always a VMA found for a write up to PAGE_SIZE below r1. That meant the bug was hidden as we continued to expand the signal frame in commit 2b0a576d15e0 ("powerpc: Add new transactional memory state to the signal context") (Feb 2013): struct rt_sigframe { struct ucontext uc; /* 0 1696 */ /* --- cacheline 13 boundary (1664 bytes) was 32 bytes ago --- */ struct ucontext uc_transact; /* 1696 1696 */ <-- /* --- cacheline 26 boundary (3328 bytes) was 64 bytes ago --- */ long unsigned int _unused[2]; /* 3392 16 */ unsigned int tramp[6]; /* 3408 24 */ struct siginfo * pinfo; /* 3432 8 */ void * puc; /* 3440 8 */ struct siginfo info; /* 3448 128 */ /* --- cacheline 27 boundary (3456 bytes) was 120 bytes ago --- */ char abigap[288]; /* 3576 288 */ /* size: 3872, cachelines: 31, members: 8 */ /* padding: 8 */ /* last cacheline: 32 bytes */ }; 3872 + 128 = 4000 And commit 573ebfa6601f ("powerpc: Increase stack redzone for 64-bit userspace to 512 bytes") (Feb 2014): struct rt_sigframe { struct ucontext uc; /* 0 1696 */ /* --- cacheline 13 boundary (1664 bytes) was 32 bytes ago --- */ struct ucontext uc_transact; /* 1696 1696 */ /* --- cacheline 26 boundary (3328 bytes) was 64 bytes ago --- */ long unsigned int _unused[2]; /* 3392 16 */ unsigned int tramp[6]; /* 3408 24 */ struct siginfo * pinfo; /* 3432 8 */ void * puc; /* 3440 8 */ struct siginfo info; /* 3448 128 */ /* --- cacheline 27 boundary (3456 bytes) was 120 bytes ago --- */ char abigap[512]; /* 3576 512 */ <-- /* size: 4096, cachelines: 32, members: 8 */ /* padding: 8 */ }; 4096 + 128 = 4224 Then finally in 2017, commit 1be7107fbe18 ("mm: larger stack guard gap, between vmas") exposed us to the existing bug, because it changed the stack VMA to be the correct/real size, meaning our stack expansion code is now triggered. Fix it by increasing the allowance to 4224 bytes. Hard-coding 4224 is obviously unsafe against future expansions of the signal frame in the same way as the existing code. We can't easily use sizeof() because the signal frame structure is not in a header. We will either fix that, or rip out all the custom stack expansion checking logic entirely. Fixes: ce48b2100785 ("powerpc: Add VSX context save/restore, ptrace and signal support") Cc: stable@vger.kernel.org # v2.6.27+ Reported-by: Tom Lane Tested-by: Daniel Axtens Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200724092528.1578671-2-mpe@ellerman.id.au Signed-off-by: Daniel Axtens Signed-off-by: Greg Kroah-Hartman

powerpc/fsl_booke: Avoid creating duplicate tlb1 entry

2020-04-24T05:57:17+00:00

[ Upstream commit aa4113340ae6c2811e046f08c2bc21011d20a072 ] In the current implementation, the call to loadcam_multi() is wrapped between switch_to_as1() and restore_to_as0() calls so, when it tries to create its own temporary AS=1 TLB1 entry, it ends up duplicating the existing one created by switch_to_as1(). Add a check to skip creating the temporary entry if already running in AS=1. Fixes: d9e1831a4202 ("powerpc/85xx: Load all early TLB entries at once") Cc: stable@vger.kernel.org # v4.4+ Signed-off-by: Laurentiu Tudor Acked-by: Scott Wood Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200123111914.2565-1-laurentiu.tudor@nxp.com Signed-off-by: Sasha Levin

powerpc: Ensure that swiotlb buffer is allocated from low memory

2020-01-12T10:22:48+00:00

[ Upstream commit 8fabc623238e68b3ac63c0dd1657bf86c1fa33af ] Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a system has more physical memory than this limit, the swiotlb buffer is not addressable because it is allocated from memblock using top-down mode. Force memblock to bottom-up mode before calling swiotlb_init() to ensure that the swiotlb buffer is DMA-able. Reported-by: Christian Zigotzky Signed-off-by: Mike Rapoport Reviewed-by: Christoph Hellwig Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20191204123524.22919-1-rppt@kernel.org Signed-off-by: Sasha Levin

powerpc/mm: Make NULL pointer deferences explicit on bad page faults.

2019-12-05T14:26:58+00:00

[ Upstream commit 49a502ea23bf9dec47f8f3c3960909ff409cd1bb ] As several other arches including x86, this patch makes it explicit that a bad page fault is a NULL pointer dereference when the fault address is lower than PAGE_SIZE In the mean time, this page makes all bad_page_fault() messages shorter so that they remain on one single line. And it prefixes them by "BUG: " so that they get easily grepped. Signed-off-by: Christophe Leroy [mpe: Avoid pr_cont()] Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin

powerpc/book3s/32: fix number of bats in p/v_block_mapped()

2019-12-05T14:26:53+00:00

[ Upstream commit e93ba1b7eb5b188c749052df7af1c90821c5f320 ] This patch fixes the loop in p_block_mapped() and v_block_mapped() to scan the entire bat_addrs[] array. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin

powerpc/64s/hash: Fix stab_rr off by one initialization

2019-11-25T14:54:00+00:00

[ Upstream commit 09b4438db13fa83b6219aee5993711a2aa2a0c64 ] This causes SLB alloation to start 1 beyond the start of the SLB. There is no real problem because after it wraps it stats behaving properly, it's just surprisig to see when looking at SLB traces. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin

powerpc/numa: improve control of topology updates

2019-06-11T10:23:58+00:00

[ Upstream commit 2d4d9b308f8f8dec68f6dbbff18c68ec7c6bd26f ] When booted with "topology_updates=no", or when "off" is written to /proc/powerpc/topology_updates, NUMA reassignments are inhibited for PRRN and VPHN events. However, migration and suspend unconditionally re-enable reassignments via start_topology_update(). This is incoherent. Check the topology_updates_enabled flag in start/stop_topology_update() so that callers of those APIs need not be aware of whether reassignments are enabled. This allows the administrative decision on reassignments to remain in force across migrations and suspensions. Signed-off-by: Nathan Lynch Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin

powerpc/fsl: Flush the branch predictor at each kernel entry (64bit)

2019-05-16T17:44:50+00:00

commit 10c5e83afd4a3f01712d97d3bb1ae34d5b74a185 upstream. In order to protect against speculation attacks on indirect branches, the branch predictor is flushed at kernel entry to protect for the following situations: - userspace process attacking another userspace process - userspace process attacking the kernel Basically when the privillege level change (i.e. the kernel is entered), the branch predictor state is flushed. Signed-off-by: Diana Craciun Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman

powerpc: Avoid code patching freed init sections

2019-05-16T17:44:50+00:00

commit 51c3c62b58b357e8d35e4cc32f7b4ec907426fe3 upstream. This stops us from doing code patching in init sections after they've been freed. In this chain: kvm_guest_init() -> kvm_use_magic_page() -> fault_in_pages_readable() -> __get_user() -> __get_user_nocheck() -> barrier_nospec(); We have a code patching location at barrier_nospec() and kvm_guest_init() is an init function. This whole chain gets inlined, so when we free the init section (hence kvm_guest_init()), this code goes away and hence should no longer be patched. We seen this as userspace memory corruption when using a memory checker while doing partition migration testing on powervm (this starts the code patching post migration via /sys/kernel/mobility/migration). In theory, it could also happen when using /sys/kernel/debug/powerpc/barrier_nospec. Signed-off-by: Michael Neuling Reviewed-by: Nicholas Piggin Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman

powerpc/numa: Suppress "VPHN is not supported" messages

2018-12-01T08:46:35+00:00

[ Upstream commit 437ccdc8ce629470babdda1a7086e2f477048cbd ] When VPHN function is not supported and during cpu hotplug event, kernel prints message 'VPHN function not supported. Disabling polling...'. Currently it prints on every hotplug event, it floods dmesg when a KVM guest tries to hotplug huge number of vcpus, let's just print once and suppress further kernel prints. Signed-off-by: Satheesh Rajendran Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin