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ALSA: hwdep: Move put_user() call out of scoped_guard() in snd_hwdep_control_ioctl()

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Clang prior to 17.0.0 has a bug in its asm goto jump scope analysis to
determine that no variables with the cleanup attribute are skipped by an
indirect jump. Instead of only checking the scope of each label that is
a possible target of each asm goto statement, it checks the scope of
every label, which can cause an error when a variable with the cleanup
attribute is used between two asm goto statements with different scopes,
even if they have completely different label targets:

  sound/core/hwdep.c:273:8: error: cannot jump from this asm goto statement to one of its possible targets
                          if (get_user(device, (int __user *)arg))
                              ^
  arch/powerpc/include/asm/uaccess.h:295:5: note: expanded from macro 'get_user'
                    __get_user(x, _gu_addr) :                             \
                    ^
  arch/powerpc/include/asm/uaccess.h:283:2: note: expanded from macro '__get_user'
          __get_user_size_allowed(__gu_val, __gu_addr, __gu_size, __gu_err);      \
          ^
  arch/powerpc/include/asm/uaccess.h:199:3: note: expanded from macro '__get_user_size_allowed'
                  __get_user_size_goto(x, ptr, size, __gus_failed);       \
                  ^
  arch/powerpc/include/asm/uaccess.h:187:10: note: expanded from macro '__get_user_size_goto'
          case 1: __get_user_asm_goto(x, (u8 __user *)ptr, label, "lbz"); break;  \
                  ^
  arch/powerpc/include/asm/uaccess.h:158:2: note: expanded from macro '__get_user_asm_goto'
          asm_volatile_goto(                                      \
          ^
  include/linux/compiler_types.h:366:33: note: expanded from macro 'asm_volatile_goto'
  #define asm_volatile_goto(x...) asm goto(x)
                                  ^
  sound/core/hwdep.c:291:9: note: possible target of asm goto statement
                                  if (put_user(device, (int __user *)arg))
                                      ^
  arch/powerpc/include/asm/uaccess.h:66:5: note: expanded from macro 'put_user'
                    __put_user(x, _pu_addr) : -EFAULT;                    \
                    ^
  arch/powerpc/include/asm/uaccess.h:52:9: note: expanded from macro '__put_user'
                                                                  \
                                                                  ^
  sound/core/hwdep.c:276:4: note: jump bypasses initialization of variable with __attribute__((cleanup))
                          scoped_guard(mutex, &register_mutex) {
                          ^
  include/linux/cleanup.h:169:20: note: expanded from macro 'scoped_guard'
          for (CLASS(_name, scope)(args),                                 \

To avoid this issue, move the put_user() call out of the scoped_guard()
scope, which allows the asm goto scope analysis to see that the variable
with the cleanup attribute will never be skipped by the asm goto
statements.

There should be no functional change because prior to the refactoring,
put_user() was not called under register_mutex, so this call does not
even need to be in the scoped_guard() in the first place.

Fixes: e6684d08cc ("ALSA: hwdep: Use guard() for locking")
Closes: https://github.com/ClangBuiltLinux/linux/issues/2003
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240301-fix-snd-hwdep-guard-v1-1-6aab033f3f83@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Nathan Chancellor 2024-03-01 10:08:22 -07:00 committed by Takashi Iwai
parent 7dba48a474
commit 72165c867f
1 changed files with 3 additions and 4 deletions
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7
sound/core/hwdep.c
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@ -288,11 +288,10 @@ static int snd_hwdep_control_ioctl(struct snd_card *card,
} }
if (device >= SNDRV_MINOR_HWDEPS) if (device >= SNDRV_MINOR_HWDEPS)
device = -1; device = -1;
if (put_user(device, (int __user *)arg))
return -EFAULT;
return 0;
} }
break; if (put_user(device, (int __user *)arg))
return -EFAULT;
return 0;
} }
case SNDRV_CTL_IOCTL_HWDEP_INFO: case SNDRV_CTL_IOCTL_HWDEP_INFO:
{ {