| Message ID | 20210420165001.3790670-1-Liam.Howlett@Oracle.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [1/3] arm64: armv8_deprecated: Fix swp_handler() signal generation | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
Hi Liam,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on arm64/for-next/core]
[also build test WARNING on arm-perf/for-next/perf xlnx/master arm/for-next soc/for-next kvmarm/next linus/master v5.12-rc8 next-20210420]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Liam-Howlett/arm64-armv8_deprecated-Fix-swp_handler-signal-generation/20210421-005252
base: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
config: arm64-allyesconfig (attached as .config)
compiler: aarch64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/96a011695861072d32851ba3a104b19106955869
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Liam-Howlett/arm64-armv8_deprecated-Fix-swp_handler-signal-generation/20210421-005252
git checkout 96a011695861072d32851ba3a104b19106955869
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=arm64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
arch/arm64/kernel/armv8_deprecated.c: In function 'swp_handler':
>> arch/arm64/kernel/armv8_deprecated.c:418:11: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
418 | else if (res = -ENXIO) /* Unaligned pointer */
| ^~~
vim +418 arch/arm64/kernel/armv8_deprecated.c
365
366 /*
367 * swp_handler logs the id of calling process, dissects the instruction, sanity
368 * checks the memory location, calls emulate_swpX for the actual operation and
369 * deals with fixup/error handling before returning
370 */
371 static int swp_handler(struct pt_regs *regs, u32 instr)
372 {
373 u32 destreg, data, type, address = 0;
374 const void __user *user_ptr;
375 int rn, rt2, res = 0;
376
377 perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
378
379 type = instr & TYPE_SWPB;
380
381 switch (aarch32_check_condition(instr, regs->pstate)) {
382 case ARM_OPCODE_CONDTEST_PASS:
383 break;
384 case ARM_OPCODE_CONDTEST_FAIL:
385 /* Condition failed - return to next instruction */
386 goto ret;
387 case ARM_OPCODE_CONDTEST_UNCOND:
388 /* If unconditional encoding - not a SWP, undef */
389 return -EFAULT;
390 default:
391 return -EINVAL;
392 }
393
394 rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET);
395 rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET);
396
397 address = (u32)regs->user_regs.regs[rn];
398 data = (u32)regs->user_regs.regs[rt2];
399 destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET);
400
401 pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
402 rn, address, destreg,
403 aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data);
404
405 /* Check access in reasonable access range for both SWP and SWPB */
406 user_ptr = (const void __user *)(unsigned long)(address & ~3);
407 if (!access_ok(user_ptr, 4)) {
408 pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n",
409 address);
410 goto e_access;
411 }
412
413 res = emulate_swpX(address, &data, type);
414 if (!res)
415 regs->user_regs.regs[destreg] = data;
416 else if (res == -EFAULT)
417 goto e_fault;
> 418 else if (res = -ENXIO) /* Unaligned pointer */
419 goto e_align;
420
421 ret:
422 if (type == TYPE_SWPB)
423 trace_instruction_emulation("swpb", regs->pc);
424 else
425 trace_instruction_emulation("swp", regs->pc);
426
427 pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
428 current->comm, (unsigned long)current->pid, regs->pc);
429
430 arm64_skip_faulting_instruction(regs, 4);
431 return 0;
432
433 e_fault:
434 pr_debug("SWP{B} emulation: access caused memory abort!\n");
435 arm64_notify_segfault(address);
436 return 0;
437
438 e_align:
439 e_access:
440 force_signal_inject(SIGSEGV, SEGV_ACCERR, address, 0);
441 return 0;
442 }
443
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
* kernel test robot <lkp@intel.com> [210420 17:22]: > Hi Liam, > > Thank you for the patch! Perhaps something to improve: > > [auto build test WARNING on arm64/for-next/core] > [also build test WARNING on arm-perf/for-next/perf xlnx/master arm/for-next soc/for-next kvmarm/next linus/master v5.12-rc8 next-20210420] > [If your patch is applied to the wrong git tree, kindly drop us a note. > And when submitting patch, we suggest to use '--base' as documented in > https://git-scm.com/docs/git-format-patch] > > url: https://github.com/0day-ci/linux/commits/Liam-Howlett/arm64-armv8_deprecated-Fix-swp_handler-signal-generation/20210421-005252 > base: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core > config: arm64-allyesconfig (attached as .config) > compiler: aarch64-linux-gcc (GCC) 9.3.0 > reproduce (this is a W=1 build): > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # https://github.com/0day-ci/linux/commit/96a011695861072d32851ba3a104b19106955869 > git remote add linux-review https://github.com/0day-ci/linux > git fetch --no-tags linux-review Liam-Howlett/arm64-armv8_deprecated-Fix-swp_handler-signal-generation/20210421-005252 > git checkout 96a011695861072d32851ba3a104b19106955869 > # save the attached .config to linux build tree > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=arm64 > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp@intel.com> > > All warnings (new ones prefixed by >>): > > arch/arm64/kernel/armv8_deprecated.c: In function 'swp_handler': > >> arch/arm64/kernel/armv8_deprecated.c:418:11: warning: suggest parentheses around assignment used as truth value [-Wparentheses] > 418 | else if (res = -ENXIO) /* Unaligned pointer */ > | ^~~ > Ah, I hadn't had the correct config enabled for this code to be compiled. I will wait for any other comments then I'll send out a v2 with this fix. Thanks, Liam
On Tue, Apr 20, 2021 at 04:50:12PM +0000, Liam Howlett wrote: > arm64_notify_segfault() was written to decide on the si_code from the > assembly emulation of the swp_handler(), but was also used for the > signal generation from failed access_ok() and unaligned instructions. > > When access_ok() fails, there is no need to search for the offending > address in the VMA space. Instead, simply set the error to SIGSEGV with > si_code SEGV_ACCERR. > > Change the return code from emulate_swpX() when there is an unaligned > pointer so the caller can differentiate from the EFAULT. It is > unnecessary to search the VMAs in the case of an unaligned pointer. > This change uses SIGSEGV and SEGV_ACCERR instead of SIGBUS to keep with > what was returned before. > > Fixes: bd35a4adc413 (arm64: Port SWP/SWPB emulation support from arm) > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> > --- > arch/arm64/kernel/armv8_deprecated.c | 20 +++++++++++++------- Can you give an example of something that is fixed by this, please? At first glance, it doesn't look like it changes the user-visible behaviour. We should also be compatible with arch/arm/ here (see set_segfault()). Will
* Will Deacon <will@kernel.org> [210422 09:01]: > On Tue, Apr 20, 2021 at 04:50:12PM +0000, Liam Howlett wrote: > > arm64_notify_segfault() was written to decide on the si_code from the > > assembly emulation of the swp_handler(), but was also used for the > > signal generation from failed access_ok() and unaligned instructions. > > > > When access_ok() fails, there is no need to search for the offending > > address in the VMA space. Instead, simply set the error to SIGSEGV with > > si_code SEGV_ACCERR. > > > > Change the return code from emulate_swpX() when there is an unaligned > > pointer so the caller can differentiate from the EFAULT. It is > > unnecessary to search the VMAs in the case of an unaligned pointer. > > This change uses SIGSEGV and SEGV_ACCERR instead of SIGBUS to keep with > > what was returned before. > > > > Fixes: bd35a4adc413 (arm64: Port SWP/SWPB emulation support from arm) > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> > > --- > > arch/arm64/kernel/armv8_deprecated.c | 20 +++++++++++++------- > > Can you give an example of something that is fixed by this, please? At first > glance, it doesn't look like it changes the user-visible behaviour. In short, when !access_ok(), don't return SEGV_MAPERR. access_ok() is defined as __range_ok() which checks if the address is a userspace address. If the access is not okay, then the return should be SEGV_ACCERR. However, if the address is above any known VMA, then the return will be SEGV_MAPERR. Isn't this a bug? Right now this particular bug is masked almost always by the fact that find_vma() will return SIGV_ACCERR unless it's abvove any known VMA, but patch 3 in this series will alter the behaviour and thus, I wanted to fix the bug here before fixing that bug. > > We should also be compatible with arch/arm/ here (see set_segfault()). Yes, the same error exists there it seems. If my solution is acceptable, I can expand it to include the same change there. Thanks, Liam
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c index 0e86e8b9cedd..f424082b3455 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -324,7 +324,7 @@ static int emulate_swpX(unsigned int address, unsigned int *data, if ((type != TYPE_SWPB) && (address & 0x3)) { /* SWP to unaligned address not permitted */ pr_debug("SWP instruction on unaligned pointer!\n"); - return -EFAULT; + return -ENXIO; } while (1) { @@ -406,15 +406,17 @@ static int swp_handler(struct pt_regs *regs, u32 instr) user_ptr = (const void __user *)(unsigned long)(address & ~3); if (!access_ok(user_ptr, 4)) { pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n", - address); - goto fault; + address); + goto e_access; } res = emulate_swpX(address, &data, type); - if (res == -EFAULT) - goto fault; - else if (res == 0) + if (!res) regs->user_regs.regs[destreg] = data; + else if (res == -EFAULT) + goto e_fault; + else if (res = -ENXIO) /* Unaligned pointer */ + goto e_align; ret: if (type == TYPE_SWPB) @@ -428,10 +430,14 @@ static int swp_handler(struct pt_regs *regs, u32 instr) arm64_skip_faulting_instruction(regs, 4); return 0; -fault: +e_fault: pr_debug("SWP{B} emulation: access caused memory abort!\n"); arm64_notify_segfault(address); + return 0; +e_align: +e_access: + force_signal_inject(SIGSEGV, SEGV_ACCERR, address, 0); return 0; }
arm64_notify_segfault() was written to decide on the si_code from the assembly emulation of the swp_handler(), but was also used for the signal generation from failed access_ok() and unaligned instructions. When access_ok() fails, there is no need to search for the offending address in the VMA space. Instead, simply set the error to SIGSEGV with si_code SEGV_ACCERR. Change the return code from emulate_swpX() when there is an unaligned pointer so the caller can differentiate from the EFAULT. It is unnecessary to search the VMAs in the case of an unaligned pointer. This change uses SIGSEGV and SEGV_ACCERR instead of SIGBUS to keep with what was returned before. Fixes: bd35a4adc413 (arm64: Port SWP/SWPB emulation support from arm) Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> --- arch/arm64/kernel/armv8_deprecated.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)