Commit e5664e23 authored by Ben Hutchings's avatar Ben Hutchings

mm/mincore.c: make mincore() more conservative (CVE-2019-5489)

parent 1894e893
......@@ -12,6 +12,7 @@ linux (4.19.37-4) UNRELEASED; urgency=medium
(CVE-2019-3846)
* mwifiex: Abort at too short BSS descriptor element
* mwifiex: Don't abort on small, spec-compliant vendor IEs
* mm/mincore.c: make mincore() more conservative (CVE-2019-5489)
[ Romain Perier ]
* [rt] Update to 4.19.37-rt20
......
From: Jiri Kosina <jkosina@suse.cz>
Date: Tue, 14 May 2019 15:41:38 -0700
Subject: mm/mincore.c: make mincore() more conservative
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit?id=f580a54bbd522f2518fd642f7d4d73ad728e5d58
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2019-5489
commit 134fca9063ad4851de767d1768180e5dede9a881 upstream.
The semantics of what mincore() considers to be resident is not
completely clear, but Linux has always (since 2.3.52, which is when
mincore() was initially done) treated it as "page is available in page
cache".
That's potentially a problem, as that [in]directly exposes
meta-information about pagecache / memory mapping state even about
memory not strictly belonging to the process executing the syscall,
opening possibilities for sidechannel attacks.
Change the semantics of mincore() so that it only reveals pagecache
information for non-anonymous mappings that belog to files that the
calling process could (if it tried to) successfully open for writing;
otherwise we'd be including shared non-exclusive mappings, which
- is the sidechannel
- is not the usecase for mincore(), as that's primarily used for data,
not (shared) text
[jkosina@suse.cz: v2]
Link: http://lkml.kernel.org/r/20190312141708.6652-2-vbabka@suse.cz
[mhocko@suse.com: restructure can_do_mincore() conditions]
Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1903062342020.19912@cbobk.fhfr.pm
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Josh Snyder <joshs@netflix.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Originally-by: Linus Torvalds <torvalds@linux-foundation.org>
Originally-by: Dominique Martinet <asmadeus@codewreck.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Cyril Hrubis <chrubis@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Daniel Gruss <daniel@gruss.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/mincore.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/mm/mincore.c b/mm/mincore.c
index fc37afe226e6..2732c8c0764c 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -169,6 +169,22 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
return 0;
}
+static inline bool can_do_mincore(struct vm_area_struct *vma)
+{
+ if (vma_is_anonymous(vma))
+ return true;
+ if (!vma->vm_file)
+ return false;
+ /*
+ * Reveal pagecache information only for non-anonymous mappings that
+ * correspond to the files the calling process could (if tried) open
+ * for writing; otherwise we'd be including shared non-exclusive
+ * mappings, which opens a side channel.
+ */
+ return inode_owner_or_capable(file_inode(vma->vm_file)) ||
+ inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
+}
+
/*
* Do a chunk of "sys_mincore()". We've already checked
* all the arguments, we hold the mmap semaphore: we should
@@ -189,8 +205,13 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v
vma = find_vma(current->mm, addr);
if (!vma || addr < vma->vm_start)
return -ENOMEM;
- mincore_walk.mm = vma->vm_mm;
end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
+ if (!can_do_mincore(vma)) {
+ unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
+ memset(vec, 1, pages);
+ return pages;
+ }
+ mincore_walk.mm = vma->vm_mm;
err = walk_page_range(addr, end, &mincore_walk);
if (err < 0)
return err;
......@@ -220,6 +220,7 @@ bugfix/all/Bluetooth-hidp-fix-buffer-overflow.patch
bugfix/all/mwifiex-fix-possible-buffer-overflows-at-parsing-bss.patch
bugfix/all/mwifiex-abort-at-too-short-bss-descriptor-element.patch
bugfix/all/mwifiex-don-t-abort-on-small-spec-compliant-vendor-ies.patch
bugfix/all/mm-mincore.c-make-mincore-more-conservative.patch
# Fix exported symbol versions
bugfix/all/module-disable-matching-missing-version-crc.patch
......
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