| Message ID | 1505975570447-568224618-4-diffsplit-thomas@m3y3r.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Sep 21, 2017 at 08:33:46AM +0200, Thomas Meyer wrote: > Remove casting the values returned by memory allocation functions like > kmalloc, kzalloc, kmem_cache_alloc, kmem_cache_zalloc etc." > Found by coccinelle spatch "api/alloc/alloc_cast.cocci" > > Signed-off-by: Thomas Meyer <thomas@m3y3r.de> > --- > > diff -u -p a/sound/pci/emu10k1/emufx.c b/sound/pci/emu10k1/emufx.c > --- a/sound/pci/emu10k1/emufx.c > +++ b/sound/pci/emu10k1/emufx.c > @@ -1218,7 +1218,7 @@ static int _snd_emu10k1_audigy_init_efx( > if (!icode) > return err; > > - icode->gpr_map = (u_int32_t __user *) kcalloc(512 + 256 + 256 + 2 * 1024, > + icode->gpr_map = kcalloc(512 + 256 + 256 + 2 * 1024, > sizeof(u_int32_t), GFP_KERNEL); And _this_ is a wonderful example of the reasons why that kind of patches is bloody bad. The code you've caught is very obviously smelly - kcalloc() does *NOT* return a userland pointer. You are whitewashing it; a major "something weird is going on here" sign is gone (something weird in that case is hopefully a set_fs(KERNEL_DS) somewhere nearby, and it is asking for careful review). FWIW, any patches of that sort anywhere near VFS are very much not welcome.
On Thu, 21 Sep 2017 19:39:15 +0200, Al Viro wrote: > > On Thu, Sep 21, 2017 at 08:33:46AM +0200, Thomas Meyer wrote: > > Remove casting the values returned by memory allocation functions like > > kmalloc, kzalloc, kmem_cache_alloc, kmem_cache_zalloc etc." > > Found by coccinelle spatch "api/alloc/alloc_cast.cocci" > > > > Signed-off-by: Thomas Meyer <thomas@m3y3r.de> > > --- > > > > diff -u -p a/sound/pci/emu10k1/emufx.c b/sound/pci/emu10k1/emufx.c > > --- a/sound/pci/emu10k1/emufx.c > > +++ b/sound/pci/emu10k1/emufx.c > > @@ -1218,7 +1218,7 @@ static int _snd_emu10k1_audigy_init_efx( > > if (!icode) > > return err; > > > > - icode->gpr_map = (u_int32_t __user *) kcalloc(512 + 256 + 256 + 2 * 1024, > > + icode->gpr_map = kcalloc(512 + 256 + 256 + 2 * 1024, > > sizeof(u_int32_t), GFP_KERNEL); > > And _this_ is a wonderful example of the reasons why that kind of > patches is bloody bad. The code you've caught is very obviously smelly - > kcalloc() does *NOT* return a userland pointer. You are whitewashing it; > a major "something weird is going on here" sign is gone (something weird > in that case is hopefully a set_fs(KERNEL_DS) somewhere nearby, and it > is asking for careful review). Right, the code touched by the patch is a really tricky one. It uses the same struct that contains __user pointer which is supposed to be filled by ioctl, but in this case, the function allocates the kernel buffer and passes it with a special flag mentioning it being a kernel buffer later. thanks, Takashi
diff -u -p a/sound/pci/emu10k1/emufx.c b/sound/pci/emu10k1/emufx.c --- a/sound/pci/emu10k1/emufx.c +++ b/sound/pci/emu10k1/emufx.c @@ -1218,7 +1218,7 @@ static int _snd_emu10k1_audigy_init_efx( if (!icode) return err; - icode->gpr_map = (u_int32_t __user *) kcalloc(512 + 256 + 256 + 2 * 1024, + icode->gpr_map = kcalloc(512 + 256 + 256 + 2 * 1024, sizeof(u_int32_t), GFP_KERNEL); if (!icode->gpr_map) goto __err_gpr; @@ -1853,7 +1853,7 @@ static int _snd_emu10k1_init_efx(struct if (!icode) return err; - icode->gpr_map = (u_int32_t __user *) kcalloc(256 + 160 + 160 + 2 * 512, + icode->gpr_map = kcalloc(256 + 160 + 160 + 2 * 512, sizeof(u_int32_t), GFP_KERNEL); if (!icode->gpr_map) goto __err_gpr;
Remove casting the values returned by memory allocation functions like kmalloc, kzalloc, kmem_cache_alloc, kmem_cache_zalloc etc." Found by coccinelle spatch "api/alloc/alloc_cast.cocci" Signed-off-by: Thomas Meyer <thomas@m3y3r.de> ---