Buildresult: powerpc-next/versatile_defconfig/arm-gcc4.9 built on Feb 4 2021, 01:04

kisskb

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Status:	OK
Date/Time:	Feb 4 2021, 01:04
Duration:	0:01:02.186878
Builder:	blade4b
Revision:	powerpc/kuap: Restore AMR after replaying soft interrupts (`006b445f18fa152c8e375abf4c68eab6d0b4afae)`
Target:	powerpc-next/versatile_defconfig/arm-gcc4.9
Branch:	powerpc-next
Compiler:	arm-gcc4.9 (arm-linux-gnueabi-gcc (GCC) 4.9.4 / GNU ld (GNU Binutils) 2.29.1.20170915)
Config:	versatile_defconfig (download)
Log:	Download original No warnings found in log. Full Log # git rev-parse -q --verify 006b445f18fa152c8e375abf4c68eab6d0b4afae^{commit} 006b445f18fa152c8e375abf4c68eab6d0b4afae already have revision, skipping fetch # git checkout -q -f -B kisskb 006b445f18fa152c8e375abf4c68eab6d0b4afae # git clean -qxdf # < git log -1 # commit 006b445f18fa152c8e375abf4c68eab6d0b4afae # Author: Alexey Kardashevskiy <aik@ozlabs.ru> # Date: Tue Feb 2 20:15:41 2021 +1100 # # powerpc/kuap: Restore AMR after replaying soft interrupts # # Since de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace # Access Protection"), user access helpers call user_{read\|write}_access_{begin\|end} # when user space access is allowed. # # Commit 890274c2dc4c ("powerpc/64s: Implement KUAP for Radix MMU") made # the mentioned helpers program a AMR special register to allow such # access for a short period of time, most of the time AMR is expected to # block user memory access by the kernel. # # Since the code accesses the user space memory, unsafe_get_user() calls # might_fault() which calls arch_local_irq_restore() if either # CONFIG_PROVE_LOCKING or CONFIG_DEBUG_ATOMIC_SLEEP is enabled. # arch_local_irq_restore() then attempts to replay pending soft # interrupts as KUAP regions have hardware interrupts enabled. # # If a pending interrupt happens to do user access (performance # interrupts do that), it enables access for a short period of time so # after returning from the replay, the user access state remains blocked # and if a user page fault happens - "Bug: Read fault blocked by AMR!" # appears and SIGSEGV is sent. # # An example trace: # Bug: Read fault blocked by AMR! # WARNING: CPU: 0 PID: 1603 at /home/aik/p/kernel/arch/powerpc/include/asm/book3s/64/kup-radix.h:145 # CPU: 0 PID: 1603 Comm: amr Not tainted 5.10.0-rc6_v5.10-rc6_a+fstn1 #24 # NIP: c00000000009ece8 LR: c00000000009ece4 CTR: 0000000000000000 # REGS: c00000000dc63560 TRAP: 0700 Not tainted (5.10.0-rc6_v5.10-rc6_a+fstn1) # MSR: 8000000000021033 <SF,ME,IR,DR,RI,LE> CR: 28002888 XER: 20040000 # CFAR: c0000000001fa928 IRQMASK: 1 # GPR00: c00000000009ece4 c00000000dc637f0 c000000002397600 000000000000001f # GPR04: c0000000020eb318 0000000000000000 c00000000dc63494 0000000000000027 # GPR08: c00000007fe4de68 c00000000dfe9180 0000000000000000 0000000000000001 # GPR12: 0000000000002000 c0000000030a0000 0000000000000000 0000000000000000 # GPR16: 0000000000000000 0000000000000000 0000000000000000 bfffffffffffffff # GPR20: 0000000000000000 c0000000134a4020 c0000000019c2218 0000000000000fe0 # GPR24: 0000000000000000 0000000000000000 c00000000d106200 0000000040000000 # GPR28: 0000000000000000 0000000000000300 c00000000dc63910 c000000001946730 # NIP __do_page_fault+0xb38/0xde0 # LR __do_page_fault+0xb34/0xde0 # Call Trace: # __do_page_fault+0xb34/0xde0 (unreliable) # handle_page_fault+0x10/0x2c # --- interrupt: 300 at strncpy_from_user+0x290/0x440 # LR = strncpy_from_user+0x284/0x440 # strncpy_from_user+0x2f0/0x440 (unreliable) # getname_flags+0x88/0x2c0 # do_sys_openat2+0x2d4/0x5f0 # do_sys_open+0xcc/0x140 # system_call_exception+0x160/0x240 # system_call_common+0xf0/0x27c # # To fix it save/restore the AMR when replaying interrupts, and also # add a check if AMR was not blocked prior to replaying interrupts. # # Originally found by syzkaller. # # Fixes: 890274c2dc4c ("powerpc/64s: Implement KUAP for Radix MMU") # Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> # Reviewed-by: Nicholas Piggin <npiggin@gmail.com> # [mpe: Use normal commit citation format and add full oops log to change log] # Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> # Link: https://lore.kernel.org/r/20210202091541.36499-1-aik@ozlabs.ru # < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-gcc --version # < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-ld --version # < git log --format=%s --max-count=1 006b445f18fa152c8e375abf4c68eab6d0b4afae # < make -s -j 24 ARCH=arm O=/kisskb/build/powerpc-next_versatile_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- versatile_defconfig # < make -s -j 24 ARCH=arm O=/kisskb/build/powerpc-next_versatile_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- help # make -s -j 24 ARCH=arm O=/kisskb/build/powerpc-next_versatile_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- olddefconfig # make -s -j 24 ARCH=arm O=/kisskb/build/powerpc-next_versatile_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- Completed OK # rm -rf /kisskb/build/powerpc-next_versatile_defconfig_arm-gcc4.9 # Build took: 0:01:02.186878

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