Messages in this thread Patch in this message | | | Date | Tue, 17 Nov 2009 14:13:14 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap |
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On Fri, 16 Oct 2009 11:55:29 -0400 Eric Paris <eparis@redhat.com> wrote:
> On Fri, 2009-10-16 at 16:43 +0100, David Howells wrote: > > Eric Paris <eparis@redhat.com> wrote: > > > > > That would still call cap_file_mmap() and wouldn't solve your problem. > > > > Hmmm... I guess I don't see the problem occur because I always run the > > programs as root. > > most likely yes, your processes are going to have CAP_SYS_RAWIO and will > happily sail through the cap_file_mmap(). > > > I would guess that cap_file_mmap() and selinux_file_mmap() are, perhaps, too > > strict. The hint shouldn't be rejected unless MAP_FIXED is also set, surely, > > but should rather be revised upwards. > > On the mmu side we don't check until the kernel has turned the hint into > a real address. Which is apparently different then where the hook was > originally placed in the nommu side. > > > Certainly, addr==NULL and !MAP_FIXED is a reasonable case to permit, even in > > tightly secured MMU and SELinux mode... After all, the manual page says: > > > > If addr is NULL, then the kernel chooses the address at which to create > > the mapping; this is the most portable method of creating a new map- > > ping. > > I agree, I think the choices are > > A) agree that we just shouldn't check the address on nommu > A1) change kconfig to not allow the setting of these > (easy to do for the LSM check, but not easy as it stands today > for the cap_file_mmap() check) > A2) change the addr_only to be a flags which indicate not to check > (my original suggestion) > A3) push the config_nommu down into the security code > (your patch) > B) actually check the address, which requires moving the hook to a > location where it has been resolved. > (graff yang's patch) > > I'll leave it up to you to determine which you like the best since you > know the implications of nommu. >
So what's the status of this issue now? Should I merge the below into 2.6.32?
Thanks.
From: David Howells <dhowells@redhat.com>
Ignore the address parameter in the various file_mmap() security checks when CONFIG_MMU=n as the address hint is ignored under those circumstances, and in any case the minimum mapping address check is pointless in NOMMU mode.
Signed-off-by: David Howells <dhowells@redhat.com> Reported-by: Graff Yang <graf.yang@analog.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
include/linux/security.h | 1 + mm/nommu.c | 2 +- security/commoncap.c | 2 ++ security/selinux/hooks.c | 2 ++ 4 files changed, 6 insertions(+), 1 deletion(-)
diff -puN include/linux/security.h~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check include/linux/security.h --- a/include/linux/security.h~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check +++ a/include/linux/security.h @@ -609,6 +609,7 @@ static inline void security_free_mnt_opt * @reqprot contains the protection requested by the application. * @prot contains the protection that will be applied by the kernel. * @flags contains the operational flags. + * @addr contains the mapping address, and should be ignored in NOMMU mode. * Return 0 if permission is granted. * @file_mprotect: * Check permissions before changing memory access permissions. diff -puN mm/nommu.c~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check mm/nommu.c --- a/mm/nommu.c~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check +++ a/mm/nommu.c @@ -974,7 +974,7 @@ static int validate_mmap_request(struct } /* allow the security API to have its say */ - ret = security_file_mmap(file, reqprot, prot, flags, addr, 0); + ret = security_file_mmap(file, reqprot, prot, flags, 0, 0); if (ret < 0) return ret; diff -puN security/commoncap.c~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check security/commoncap.c --- a/security/commoncap.c~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check +++ a/security/commoncap.c @@ -1005,6 +1005,7 @@ int cap_file_mmap(struct file *file, uns { int ret = 0; +#ifdef CONFIG_MMU if (addr < dac_mmap_min_addr) { ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO, SECURITY_CAP_AUDIT); @@ -1012,5 +1013,6 @@ int cap_file_mmap(struct file *file, uns if (ret == 0) current->flags |= PF_SUPERPRIV; } +#endif return ret; } diff -puN security/selinux/hooks.c~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check security/selinux/hooks.c --- a/security/selinux/hooks.c~nommu-ignore-the-address-parameter-in-the-file_mmap-security-check +++ a/security/selinux/hooks.c @@ -3046,6 +3046,7 @@ static int selinux_file_mmap(struct file unsigned long addr, unsigned long addr_only) { int rc = 0; +#ifdef CONFIG_MMU u32 sid = current_sid(); /* @@ -3060,6 +3061,7 @@ static int selinux_file_mmap(struct file if (rc) return rc; } +#endif /* do DAC check on address space usage */ rc = cap_file_mmap(file, reqprot, prot, flags, addr, addr_only); _
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