Messages in this thread |  | | | Date | Thu, 15 Oct 2009 11:45:07 +0800 | | Subject | Re: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap | | From | graff yang <> |
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Hi, David,
Your patch works both with SELINUX enabled or disabled. But, how to prevent the address that attempting to be mapped to be lower than CONFIG_LSM_MMAP_MIN_ADDR/CONFIG_DEFAULT_MMAP_MIN_ADDR? This is what the security_file_mmap() is doing and mmu's do_mmap_pgoff() has implemented.
On Thu, Oct 15, 2009 at 10:21 AM, graff yang <graff.yang@gmail.com> wrote: > Hi, David, > Thanks your patch, I will test it. > > > On Wed, Oct 14, 2009 at 10:08 PM, David Howells <dhowells@redhat.com> wrote: >> <graff.yang@gmail.com> wrote: >> >>> The original code calling security_file_mmap() use user's hint address >>> as it's 5th argument(addr). This is improper, as the hint address may be >>> NULL. >>> In this case, the security_file_mmap() may incorrectly return -EPERM. >>> >>> This patch moved the calling of security_file_mmap() out of >>> validate_mmap_request() to do_mmap_pgoff(), and call this >>> security API with the address that attempting to mmap. >> >> I think this is the wrong approach. Firstly, the hint is cleared in NOMMU >> mode, and secondly, I think that the check against the minimum LSM address is >> pointless in NOMMU mode too. >> >> So I think the attached patch is a better approach. >> >> David >> --- >> From: David Howells <dhowells@redhat.com> >> >> NOMMU: Ignore the address parameter in the file_mmap() security check >> >> 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> >> --- >> >> include/linux/security.h | 1 + >> mm/nommu.c | 2 +- >> security/commoncap.c | 2 ++ >> security/selinux/hooks.c | 2 ++ >> 4 files changed, 6 insertions(+), 1 deletions(-) >> >> >> diff --git a/include/linux/security.h b/include/linux/security.h >> index 239e40d..0583f16 100644 >> --- a/include/linux/security.h >> +++ b/include/linux/security.h >> @@ -593,6 +593,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) >> * @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 --git a/mm/nommu.c b/mm/nommu.c >> index 3c3b4b2..cfea46c 100644 >> --- a/mm/nommu.c >> +++ b/mm/nommu.c >> @@ -974,7 +974,7 @@ static int validate_mmap_request(struct file *file, >> } >> >> /* 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 --git a/security/commoncap.c b/security/commoncap.c >> index fe30751..ac1f745 100644 >> --- a/security/commoncap.c >> +++ b/security/commoncap.c >> @@ -1005,6 +1005,7 @@ int cap_file_mmap(struct file *file, unsigned long reqprot, >> { >> 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, unsigned long reqprot, >> if (ret == 0) >> current->flags |= PF_SUPERPRIV; >> } >> +#endif >> return ret; >> } >> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c >> index bb230d5..93d61f8 100644 >> --- a/security/selinux/hooks.c >> +++ b/security/selinux/hooks.c >> @@ -3046,6 +3046,7 @@ static int selinux_file_mmap(struct file *file, unsigned long reqprot, >> 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 *file, unsigned long reqprot, >> if (rc) >> return rc; >> } >> +#endif >> >> /* do DAC check on address space usage */ >> rc = cap_file_mmap(file, reqprot, prot, flags, addr, addr_only); >> > > > > -- > -Graff >
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