Messages in this thread | | | From | Chris Evans <> | Subject | Re: [PATCH][RFC] 2.5.42: remove capable(CAP_SYS_RAWIO) check from open_kmem | Date | Thu, 17 Oct 2002 12:32:31 +0100 |
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Hi,
No, please DON'T apply.
If /dev/mem and /dev/kmem are only protected by filesystem permissions, then:
1) Ownership of either will confer CAP_SYS_RAWIO 2) CAP_DAC_OVERRIDE, etc. will confer CAP_SYS_RAWIO 3) Ability to mknod() one of the these will confer CAP_SYS_RAWIO (I think to make one you only need CAP_SYS_ADMIN, could be wrong).
CAP_SYS_RAWIO is extremely dangerous and must not be leverageable via other system capabilities or filesystem permissions.
There are many people who have systems with elaborate security setups where root access is limited in what it can do. If we allow a root user to get CAP_SYS_RAWIO easily, this is lost.
Cheers Chris
Quoting Olaf Dietsche <olaf.dietsche#list.linux-kernel@t-online.de>:
> Olaf Dietsche <olaf.dietsche#list.linux-kernel@t-online.de> writes: > > > In drivers/char/mem.c there's open_port(), which is used as open_mem() > > and open_kmem() as well. I don't see the benefit of this, since > > /dev/mem and /dev/kmem are already protected by filesystem > > permissions. > > > > mem.c, line 526: > > static int open_port(struct inode * inode, struct file * filp) > > { > > return capable(CAP_SYS_RAWIO) ? 0 : -EPERM; > > } > > > > If anyone knows, why this is done this way, please let me > > know. Otherwise, I suggest the patch below. > > I haven't got a convincing answer against this patch, so far. The > patch applies to 2.5.43 as well. > Linus, please apply. > > Regards, Olaf. > > --- a/drivers/char/mem.c Sat Oct 5 18:44:55 2002 > +++ b/drivers/char/mem.c Sun Oct 13 13:59:25 2002 > @@ -533,15 +533,12 @@ > #define full_lseek null_lseek > #define write_zero write_null > #define read_full read_zero > -#define open_mem open_port > -#define open_kmem open_mem > > static struct file_operations mem_fops = { > llseek: memory_lseek, > read: read_mem, > write: write_mem, > mmap: mmap_mem, > - open: open_mem, > }; > > static struct file_operations kmem_fops = { > @@ -549,7 +546,6 @@ > read: read_kmem, > write: write_kmem, > mmap: mmap_kmem, > - open: open_kmem, > }; > > static struct file_operations null_fops = { > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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