Messages in this thread | | | Subject | Re: [PATCH 2.6.32 19/38] [PATCH 19/38] pagemap: hide physical addresses from non-privileged users | From | Konstantin Khlebnikov <> | Date | Mon, 30 Nov 2015 14:49:59 +0300 |
| |
On 30.11.2015 14:30, Willy Tarreau wrote: > On Mon, Nov 30, 2015 at 08:01:36AM +0100, Willy Tarreau wrote: >> >On Mon, Nov 30, 2015 at 01:54:22AM +0000, Ben Hutchings wrote: >>> > >On Sun, 2015-11-29 at 22:47 +0100, Willy Tarreau wrote: >>> > >This is wrong; see >>> > ><https://marc.info/?l=linux-api&m=143144321020852&w=2>. >> > >> >Damned, and I now remember this discussion. The worst thing is that >> >I purposely booted a machine to test the fix and was happy with it, >> >I forgot this point:-( >> > >>> > >For 2.6.32 perhaps you could retain the capability check at open time >>> > >but store the result in private state for use at read time. >> > >> >I'll see if it is possible to opencode security_capable() with 2.6.32's >> >infrastructure, and how far this brings us. Or maybe we should even drop >> >this one completely and leave pagemap readable only for superuser on >> >2.6.32, it doesn't seem to be that big of a deal either. > It was easy enough to open-code security_capable() in the end. I've > tested this version which works fine for me here. If that's OK for you > I'll emit an -rc2 with the last two patches. > > Thanks, > Willy > > > 0001-pagemap-hide-physical-addresses-from-non-privileged-.patch > > > From fde24678af1b04712144457512afbc16fd71b252 Mon Sep 17 00:00:00 2001 > From: Konstantin Khlebnikov<khlebnikov@yandex-team.ru> > Date: Tue, 8 Sep 2015 15:00:07 -0700 > Subject: pagemap: hide physical addresses from non-privileged users > > commit 1c90308e7a77af6742a97d1021cca923b23b7f0d upstream. > > This patch makes pagemap readable for normal users and hides physical > addresses from them. For some use-cases PFN isn't required at all. > > Seehttp://lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@shutemov.name > > Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace") > Signed-off-by: Konstantin Khlebnikov<khlebnikov@yandex-team.ru> > Cc: Naoya Horiguchi<n-horiguchi@ah.jp.nec.com> > Reviewed-by: Mark Williamson<mwilliamson@undo-software.com> > Tested-by: Mark Williamson<mwilliamson@undo-software.com> > Signed-off-by: Andrew Morton<akpm@linux-foundation.org> > Signed-off-by: Linus Torvalds<torvalds@linux-foundation.org> > [bwh: Backported to 3.2: > - Add the same check in the places where we look up a PFN > - Add struct pagemapread * parameters where necessary > - Open-code file_ns_capable() > - Delete pagemap_open() entirely, as it would always return 0] > Signed-off-by: Ben Hutchings<ben@decadent.org.uk> > (cherry picked from commit b1fb185f26e85f76e3ac6ce557398d78797c9684) > [wt: adjusted context, no pagemap_hugetlb_range() in 2.6.32, open-coded > security_capable(). Tested OK. ] > Signed-off-by: Willy Tarreau<w@1wt.eu> > --- > fs/proc/task_mmu.c | 21 ++++++++------------- > 1 file changed, 8 insertions(+), 13 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 73db5a6..24d3602 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -8,6 +8,7 @@ > #include <linux/mempolicy.h> > #include <linux/swap.h> > #include <linux/swapops.h> > +#include <linux/security.h> > > #include <asm/elf.h> > #include <asm/uaccess.h> > @@ -539,6 +540,7 @@ const struct file_operations proc_clear_refs_operations = { > > struct pagemapread { > u64 __user *out, *end; > + bool show_pfn; > }; > > #define PM_ENTRY_BYTES sizeof(u64) > @@ -589,14 +591,14 @@ static u64 swap_pte_to_pagemap_entry(pte_t pte) > return swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT); > } > > -static u64 pte_to_pagemap_entry(pte_t pte) > +static u64 pte_to_pagemap_entry(struct pagemapread *pm, pte_t pte) > { > u64 pme = 0; > if (is_swap_pte(pte)) > pme = PM_PFRAME(swap_pte_to_pagemap_entry(pte)) > | PM_PSHIFT(PAGE_SHIFT) | PM_SWAP; > else if (pte_present(pte)) > - pme = PM_PFRAME(pte_pfn(pte)) > + pme = (pm->show_pfn ? PM_PFRAME(pte_pfn(pte)) : 0) > | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT; > return pme; > } > @@ -624,7 +626,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > if (vma && (vma->vm_start <= addr) && > !is_vm_hugetlb_page(vma)) { > pte = pte_offset_map(pmd, addr); > - pfn = pte_to_pagemap_entry(*pte); > + pfn = pte_to_pagemap_entry(pm, *pte); > /* unmap before userspace copy */ > pte_unmap(pte); > } > @@ -695,6 +697,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > if (!count) > goto out_task; > > + /* do not disclose physical addresses: attack vector */ > + pm.show_pfn = !cap_capable(current, file->f_cred, CAP_SYS_ADMIN, SECURITY_CAP_AUDIT); > +
At first sight this is confusing... but correct. It really returns zero for success, unlike to new file_ns_capable which returns bool true.
The rest looks good too.
> mm = get_task_mm(task); > if (!mm) > goto out_task; > @@ -773,19 +778,9 @@ out: > return ret; > } > > -static int pagemap_open(struct inode *inode, struct file *file) > -{ > - /* do not disclose physical addresses to unprivileged > - userspace (closes a rowhammer attack vector) */ > - if (!capable(CAP_SYS_ADMIN)) > - return -EPERM; > - return 0; > -} > - > const struct file_operations proc_pagemap_operations = { > .llseek = mem_lseek, /* borrow this */ > .read = pagemap_read, > - .open = pagemap_open, > }; > #endif /* CONFIG_PROC_PAGE_MONITOR */ > > -- 1.7.12.1 >
-- Konstantin
| |