Buildresult: powerpc-next/powerpc-allnoconfig/powerpc-gcc4.6 built on May 11 2018, 23:53

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Status:	OK
Date/Time:	May 11 2018, 23:53
Duration:	0:00:15.251522
Builder:	ka3
Revision:	powerpc: Check address limit on user-mode return (TIF_FSCHECK) (`486b416bc468d6a49e3c032b79f41485a7f3961b)`
Target:	powerpc-next/powerpc-allnoconfig/powerpc-gcc4.6
Branch:	powerpc-next
Compiler:	powerpc-gcc4.6 (powerpc-linux-gcc (GCC) 4.6.3)
Config:	allnoconfig (download)
Log:	Download original Possible warnings (1) kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized] Full Log # git rev-parse -q --verify 486b416bc468d6a49e3c032b79f41485a7f3961b^{commit} 486b416bc468d6a49e3c032b79f41485a7f3961b already have revision, skipping fetch # git checkout -q -f -B kisskb 486b416bc468d6a49e3c032b79f41485a7f3961b # git clean -qxdf # < git log -1 # commit 486b416bc468d6a49e3c032b79f41485a7f3961b # Author: Michael Ellerman <mpe@ellerman.id.au> # Date: Wed Nov 22 12:15:42 2017 +1100 # # powerpc: Check address limit on user-mode return (TIF_FSCHECK) # # set_fs() sets the addr_limit, which is used in access_ok() to # determine if an address is a user or kernel address. # # Some code paths use set_fs() to temporarily elevate the addr_limit so # that kernel code can read/write kernel memory as if it were user # memory. That is fine as long as the code can't ever return to # userspace with the addr_limit still elevated. # # If that did happen, then userspace can read/write kernel memory as if # it were user memory, eg. just with write(2). In case it's not clear, # that is very bad. It has also happened in the past due to bugs. # # Commit 5ea0727b163c ("x86/syscalls: Check address limit on user-mode # return") added a mechanism to check the addr_limit value before # returning to userspace. Any call to set_fs() sets a thread flag, # TIF_FSCHECK, and if we see that on the return to userspace we go out # of line to check that the addr_limit value is not elevated. # # For further info see the above commit, as well as: # https://lwn.net/Articles/722267/ # https://bugs.chromium.org/p/project-zero/issues/detail?id=990 # # Verified to work on 64-bit Book3S using a POC that objdumps the system # call handler, and a modified lkdtm_CORRUPT_USER_DS() that doesn't kill # the caller. # # Before: # $ sudo ./test-tif-fscheck # ... # 0000000000000000 <.data>: # 0: e1 f7 8a 79 rldicl. r10,r12,30,63 # 4: 80 03 82 40 bne 0x384 # 8: 00 40 8a 71 andi. r10,r12,16384 # c: 78 0b 2a 7c mr r10,r1 # 10: 10 fd 21 38 addi r1,r1,-752 # 14: 08 00 c2 41 beq- 0x1c # 18: 58 09 2d e8 ld r1,2392(r13) # 1c: 00 00 41 f9 std r10,0(r1) # 20: 70 01 61 f9 std r11,368(r1) # 24: 78 01 81 f9 std r12,376(r1) # 28: 70 00 01 f8 std r0,112(r1) # 2c: 78 00 41 f9 std r10,120(r1) # 30: 20 00 82 41 beq 0x50 # 34: a6 42 4c 7d mftb r10 # # After: # # $ sudo ./test-tif-fscheck # Killed # # And in dmesg: # Invalid address limit on user-mode return # WARNING: CPU: 1 PID: 3689 at ../include/linux/syscalls.h:260 do_notify_resume+0x140/0x170 # ... # NIP [c00000000001ee50] do_notify_resume+0x140/0x170 # LR [c00000000001ee4c] do_notify_resume+0x13c/0x170 # Call Trace: # do_notify_resume+0x13c/0x170 (unreliable) # ret_from_except_lite+0x70/0x74 # # Performance overhead is essentially zero in the usual case, because # the bit is checked as part of the existing _TIF_USER_WORK_MASK check. # # Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> # < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version # < git log --format=%s --max-count=1 486b416bc468d6a49e3c032b79f41485a7f3961b # < make -s -j 80 ARCH=powerpc O=/kisskb/build/powerpc-next_powerpc-allnoconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- allnoconfig # make -s -j 80 ARCH=powerpc O=/kisskb/build/powerpc-next_powerpc-allnoconfig_powerpc CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- /kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl': /kisskb/src/kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized] Completed OK # rm -rf /kisskb/build/powerpc-next_powerpc-allnoconfig_powerpc # Build took: 0:00:15.251522

© Michael Ellerman 2006-2018.