* arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining?
@ 2026-09-18 18:19 kernel test robot
0 siblings, 0 replies; 3+ messages in thread
From: kernel test robot @ 2026-09-18 18:19 UTC (permalink / raw)
To: oe-kbuild; +Cc: lkp, Dan Carpenter
BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
CC: linux-kernel@vger.kernel.org
TO: Deepak Gupta <debug@rivosinc.com>
CC: Paul Walmsley <pjw@kernel.org>
CC: Andy Chiu <andy.chiu@sifive.com>
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: f259f446f5198d98e13756d2cd531812a0ad3064
commit: 66c9c713de597f9b40a319ebda4d3466ce2cdff0 riscv/signal: save and restore the shadow stack on a signal
date: 8 months ago
:::::: branch date: 2 hours ago
:::::: commit date: 8 months ago
config: riscv-randconfig-r2201-20260918 (https://download.01.org/0day-ci/archive/20260918/202609182005.wS9nDDeW-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 9.5.0
smatch: v0.5.0-9187-g5189e3fb
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Fixes: 66c9c713de59 ("riscv/signal: save and restore the shadow stack on a signal")
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202609182005.wS9nDDeW-lkp@intel.com/
New smatch warnings:
arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining?
Old smatch warnings:
arch/riscv/kernel/signal.c:52 restore_fp_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:66 save_fp_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:132 __restore_v_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:142 __restore_v_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:228 restore_sigcontext() warn: maybe return -EFAULT instead of the bytes remaining?
vim +196 arch/riscv/kernel/signal.c
66c9c713de597f Deepak Gupta 2026-01-25 173
66c9c713de597f Deepak Gupta 2026-01-25 174 static long __restore_cfiss_state(struct pt_regs *regs, void __user *sc_cfi)
66c9c713de597f Deepak Gupta 2026-01-25 175 {
66c9c713de597f Deepak Gupta 2026-01-25 176 struct __sc_riscv_cfi_state __user *state = sc_cfi;
66c9c713de597f Deepak Gupta 2026-01-25 177 unsigned long ss_ptr = 0;
66c9c713de597f Deepak Gupta 2026-01-25 178 long err;
66c9c713de597f Deepak Gupta 2026-01-25 179
66c9c713de597f Deepak Gupta 2026-01-25 180 /*
66c9c713de597f Deepak Gupta 2026-01-25 181 * Restore shadow stack as a form of token stored on the shadow stack itself as a safe
66c9c713de597f Deepak Gupta 2026-01-25 182 * way to restore.
66c9c713de597f Deepak Gupta 2026-01-25 183 * A token on the shadow stack gives the following properties:
66c9c713de597f Deepak Gupta 2026-01-25 184 * - Safe save and restore for shadow stack switching. Any save of shadow stack
66c9c713de597f Deepak Gupta 2026-01-25 185 * must have saved a token on shadow stack. Similarly any restore of shadow
66c9c713de597f Deepak Gupta 2026-01-25 186 * stack must check the token before restore. Since writing to a shadow stack with
66c9c713de597f Deepak Gupta 2026-01-25 187 * the address of shadow stack itself is not easily allowed, a restore without a save
66c9c713de597f Deepak Gupta 2026-01-25 188 * is quite difficult for an attacker to perform.
66c9c713de597f Deepak Gupta 2026-01-25 189 * - A natural break. A token in the shadow stack provides a natural break in shadow stack
66c9c713de597f Deepak Gupta 2026-01-25 190 * So a single linear range can be bucketed into different shadow stack segments.
66c9c713de597f Deepak Gupta 2026-01-25 191 * sspopchk will detect the condition and fault to kernel as a sw check exception.
66c9c713de597f Deepak Gupta 2026-01-25 192 */
66c9c713de597f Deepak Gupta 2026-01-25 193 err = __copy_from_user(&ss_ptr, &state->ss_ptr, sizeof(unsigned long));
66c9c713de597f Deepak Gupta 2026-01-25 194
66c9c713de597f Deepak Gupta 2026-01-25 195 if (unlikely(err))
66c9c713de597f Deepak Gupta 2026-01-25 @196 return err;
66c9c713de597f Deepak Gupta 2026-01-25 197
66c9c713de597f Deepak Gupta 2026-01-25 198 return restore_user_shstk(current, ss_ptr);
66c9c713de597f Deepak Gupta 2026-01-25 199 }
66c9c713de597f Deepak Gupta 2026-01-25 200
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread* arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining?
@ 2026-02-19 7:07 ` Dan Carpenter
0 siblings, 0 replies; 3+ messages in thread
From: kernel test robot @ 2026-02-15 23:56 UTC (permalink / raw)
To: oe-kbuild; +Cc: lkp, Dan Carpenter
BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
CC: linux-kernel@vger.kernel.org
TO: Deepak Gupta <debug@rivosinc.com>
CC: Paul Walmsley <pjw@kernel.org>
CC: Andy Chiu <andy.chiu@sifive.com>
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 26a4cfaff82a2dcb810f6bfd5f4842f9b6046c8a
commit: 66c9c713de597f9b40a319ebda4d3466ce2cdff0 riscv/signal: save and restore the shadow stack on a signal
date: 3 weeks ago
:::::: branch date: 5 hours ago
:::::: commit date: 3 weeks ago
config: riscv-randconfig-r073-20260216 (https://download.01.org/0day-ci/archive/20260216/202602160730.QsdCT9Zp-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 13.4.0
smatch version: v0.5.0-8994-gd50c5a4c
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202602160730.QsdCT9Zp-lkp@intel.com/
New smatch warnings:
arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining?
Old smatch warnings:
arch/riscv/kernel/signal.c:52 restore_fp_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:66 save_fp_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:132 __restore_v_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:142 __restore_v_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:228 restore_sigcontext() warn: maybe return -EFAULT instead of the bytes remaining?
vim +196 arch/riscv/kernel/signal.c
66c9c713de597f Deepak Gupta 2026-01-25 173
66c9c713de597f Deepak Gupta 2026-01-25 174 static long __restore_cfiss_state(struct pt_regs *regs, void __user *sc_cfi)
66c9c713de597f Deepak Gupta 2026-01-25 175 {
66c9c713de597f Deepak Gupta 2026-01-25 176 struct __sc_riscv_cfi_state __user *state = sc_cfi;
66c9c713de597f Deepak Gupta 2026-01-25 177 unsigned long ss_ptr = 0;
66c9c713de597f Deepak Gupta 2026-01-25 178 long err;
66c9c713de597f Deepak Gupta 2026-01-25 179
66c9c713de597f Deepak Gupta 2026-01-25 180 /*
66c9c713de597f Deepak Gupta 2026-01-25 181 * Restore shadow stack as a form of token stored on the shadow stack itself as a safe
66c9c713de597f Deepak Gupta 2026-01-25 182 * way to restore.
66c9c713de597f Deepak Gupta 2026-01-25 183 * A token on the shadow stack gives the following properties:
66c9c713de597f Deepak Gupta 2026-01-25 184 * - Safe save and restore for shadow stack switching. Any save of shadow stack
66c9c713de597f Deepak Gupta 2026-01-25 185 * must have saved a token on shadow stack. Similarly any restore of shadow
66c9c713de597f Deepak Gupta 2026-01-25 186 * stack must check the token before restore. Since writing to a shadow stack with
66c9c713de597f Deepak Gupta 2026-01-25 187 * the address of shadow stack itself is not easily allowed, a restore without a save
66c9c713de597f Deepak Gupta 2026-01-25 188 * is quite difficult for an attacker to perform.
66c9c713de597f Deepak Gupta 2026-01-25 189 * - A natural break. A token in the shadow stack provides a natural break in shadow stack
66c9c713de597f Deepak Gupta 2026-01-25 190 * So a single linear range can be bucketed into different shadow stack segments.
66c9c713de597f Deepak Gupta 2026-01-25 191 * sspopchk will detect the condition and fault to kernel as a sw check exception.
66c9c713de597f Deepak Gupta 2026-01-25 192 */
66c9c713de597f Deepak Gupta 2026-01-25 193 err = __copy_from_user(&ss_ptr, &state->ss_ptr, sizeof(unsigned long));
66c9c713de597f Deepak Gupta 2026-01-25 194
66c9c713de597f Deepak Gupta 2026-01-25 195 if (unlikely(err))
66c9c713de597f Deepak Gupta 2026-01-25 @196 return err;
66c9c713de597f Deepak Gupta 2026-01-25 197
66c9c713de597f Deepak Gupta 2026-01-25 198 return restore_user_shstk(current, ss_ptr);
66c9c713de597f Deepak Gupta 2026-01-25 199 }
66c9c713de597f Deepak Gupta 2026-01-25 200
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread* arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining?
@ 2026-02-19 7:07 ` Dan Carpenter
0 siblings, 0 replies; 3+ messages in thread
From: Dan Carpenter @ 2026-02-19 7:07 UTC (permalink / raw)
To: oe-kbuild, Deepak Gupta
Cc: lkp, oe-kbuild-all, linux-kernel, Paul Walmsley, Andy Chiu
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 26a4cfaff82a2dcb810f6bfd5f4842f9b6046c8a
commit: 66c9c713de597f9b40a319ebda4d3466ce2cdff0 riscv/signal: save and restore the shadow stack on a signal
config: riscv-randconfig-r073-20260216 (https://download.01.org/0day-ci/archive/20260216/202602160730.QsdCT9Zp-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 13.4.0
smatch version: v0.5.0-8994-gd50c5a4c
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202602160730.QsdCT9Zp-lkp@intel.com/
New smatch warnings:
arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining?
Old smatch warnings:
arch/riscv/kernel/signal.c:52 restore_fp_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:66 save_fp_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:132 __restore_v_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:142 __restore_v_state() warn: maybe return -EFAULT instead of the bytes remaining?
arch/riscv/kernel/signal.c:228 restore_sigcontext() warn: maybe return -EFAULT instead of the bytes remaining?
vim +196 arch/riscv/kernel/signal.c
66c9c713de597f Deepak Gupta 2026-01-25 174 static long __restore_cfiss_state(struct pt_regs *regs, void __user *sc_cfi)
66c9c713de597f Deepak Gupta 2026-01-25 175 {
66c9c713de597f Deepak Gupta 2026-01-25 176 struct __sc_riscv_cfi_state __user *state = sc_cfi;
66c9c713de597f Deepak Gupta 2026-01-25 177 unsigned long ss_ptr = 0;
66c9c713de597f Deepak Gupta 2026-01-25 178 long err;
66c9c713de597f Deepak Gupta 2026-01-25 179
66c9c713de597f Deepak Gupta 2026-01-25 180 /*
66c9c713de597f Deepak Gupta 2026-01-25 181 * Restore shadow stack as a form of token stored on the shadow stack itself as a safe
66c9c713de597f Deepak Gupta 2026-01-25 182 * way to restore.
66c9c713de597f Deepak Gupta 2026-01-25 183 * A token on the shadow stack gives the following properties:
66c9c713de597f Deepak Gupta 2026-01-25 184 * - Safe save and restore for shadow stack switching. Any save of shadow stack
66c9c713de597f Deepak Gupta 2026-01-25 185 * must have saved a token on shadow stack. Similarly any restore of shadow
66c9c713de597f Deepak Gupta 2026-01-25 186 * stack must check the token before restore. Since writing to a shadow stack with
66c9c713de597f Deepak Gupta 2026-01-25 187 * the address of shadow stack itself is not easily allowed, a restore without a save
66c9c713de597f Deepak Gupta 2026-01-25 188 * is quite difficult for an attacker to perform.
66c9c713de597f Deepak Gupta 2026-01-25 189 * - A natural break. A token in the shadow stack provides a natural break in shadow stack
66c9c713de597f Deepak Gupta 2026-01-25 190 * So a single linear range can be bucketed into different shadow stack segments.
66c9c713de597f Deepak Gupta 2026-01-25 191 * sspopchk will detect the condition and fault to kernel as a sw check exception.
66c9c713de597f Deepak Gupta 2026-01-25 192 */
66c9c713de597f Deepak Gupta 2026-01-25 193 err = __copy_from_user(&ss_ptr, &state->ss_ptr, sizeof(unsigned long));
66c9c713de597f Deepak Gupta 2026-01-25 194
66c9c713de597f Deepak Gupta 2026-01-25 195 if (unlikely(err))
66c9c713de597f Deepak Gupta 2026-01-25 @196 return err;
A lot of code in signal.c used to return nonsense values because it's
highly optimized and the caller handles it. As in:
return __copy_from_user();
But this code doesn't feel very optimized, honestly, and I bet
returning -EFAULT doesn't hurt anything. I think it would be faster
to get rid of the ret variable and do:
if (__copy_from_user())
return -EFAULT;
My brief and bogus testing seems to show a slight speed up
probably based on the smaller stack size.
66c9c713de597f Deepak Gupta 2026-01-25 197
66c9c713de597f Deepak Gupta 2026-01-25 198 return restore_user_shstk(current, ss_ptr);
66c9c713de597f Deepak Gupta 2026-01-25 199 }
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-09-18 18:19 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-18 18:19 arch/riscv/kernel/signal.c:196 __restore_cfiss_state() warn: maybe return -EFAULT instead of the bytes remaining? kernel test robot
-- strict thread matches above, loose matches on Subject: below --
2026-02-15 23:56 kernel test robot
2026-02-19 7:07 ` Dan Carpenter
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.