107 lines
3.9 KiB
Diff
107 lines
3.9 KiB
Diff
From: Willy Tarreau <w@1wt.eu>
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Date: Fri, 11 May 2018 08:11:44 +0200
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Subject: proc: do not access cmdline nor environ from file-backed areas
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Origin: https://git.kernel.org/linus/7f7ccc2ccc2e70c6054685f5e3522efa81556830
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-1120
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proc_pid_cmdline_read() and environ_read() directly access the target
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process' VM to retrieve the command line and environment. If this
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process remaps these areas onto a file via mmap(), the requesting
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process may experience various issues such as extra delays if the
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underlying device is slow to respond.
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Let's simply refuse to access file-backed areas in these functions.
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For this we add a new FOLL_ANON gup flag that is passed to all calls
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to access_remote_vm(). The code already takes care of such failures
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(including unmapped areas). Accesses via /proc/pid/mem were not
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changed though.
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This was assigned CVE-2018-1120.
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Note for stable backports: the patch may apply to kernels prior to 4.11
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but silently miss one location; it must be checked that no call to
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access_remote_vm() keeps zero as the last argument.
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Reported-by: Qualys Security Advisory <qsa@qualys.com>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Andy Lutomirski <luto@amacapital.net>
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Cc: Oleg Nesterov <oleg@redhat.com>
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Cc: stable@vger.kernel.org
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Signed-off-by: Willy Tarreau <w@1wt.eu>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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fs/proc/base.c | 8 ++++----
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include/linux/mm.h | 1 +
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mm/gup.c | 3 +++
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3 files changed, 8 insertions(+), 4 deletions(-)
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diff --git a/fs/proc/base.c b/fs/proc/base.c
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index 1b2ede6abcdf..1a76d751cf3c 100644
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--- a/fs/proc/base.c
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+++ b/fs/proc/base.c
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@@ -261,7 +261,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
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* Inherently racy -- command line shares address space
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* with code and data.
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*/
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- rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);
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+ rv = access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_ANON);
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if (rv <= 0)
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goto out_free_page;
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@@ -279,7 +279,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
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int nr_read;
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_count = min3(count, len, PAGE_SIZE);
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- nr_read = access_remote_vm(mm, p, page, _count, 0);
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+ nr_read = access_remote_vm(mm, p, page, _count, FOLL_ANON);
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if (nr_read < 0)
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rv = nr_read;
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if (nr_read <= 0)
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@@ -325,7 +325,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
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bool final;
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_count = min3(count, len, PAGE_SIZE);
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- nr_read = access_remote_vm(mm, p, page, _count, 0);
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+ nr_read = access_remote_vm(mm, p, page, _count, FOLL_ANON);
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if (nr_read < 0)
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rv = nr_read;
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if (nr_read <= 0)
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@@ -946,7 +946,7 @@ static ssize_t environ_read(struct file *file, char __user *buf,
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max_len = min_t(size_t, PAGE_SIZE, count);
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this_len = min(max_len, this_len);
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- retval = access_remote_vm(mm, (env_start + src), page, this_len, 0);
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+ retval = access_remote_vm(mm, (env_start + src), page, this_len, FOLL_ANON);
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if (retval <= 0) {
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ret = retval;
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diff --git a/include/linux/mm.h b/include/linux/mm.h
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index 1ac1f06a4be6..c080af584ddd 100644
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--- a/include/linux/mm.h
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+++ b/include/linux/mm.h
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@@ -2493,6 +2493,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
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#define FOLL_MLOCK 0x1000 /* lock present pages */
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#define FOLL_REMOTE 0x2000 /* we are working on non-current tsk/mm */
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#define FOLL_COW 0x4000 /* internal GUP flag */
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+#define FOLL_ANON 0x8000 /* don't do file mappings */
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static inline int vm_fault_to_errno(int vm_fault, int foll_flags)
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{
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diff --git a/mm/gup.c b/mm/gup.c
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index 76af4cfeaf68..541904a7c60f 100644
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--- a/mm/gup.c
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+++ b/mm/gup.c
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@@ -544,6 +544,9 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
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if (vm_flags & (VM_IO | VM_PFNMAP))
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return -EFAULT;
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+ if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
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+ return -EFAULT;
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+
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if (write) {
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if (!(vm_flags & VM_WRITE)) {
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if (!(gup_flags & FOLL_FORCE))
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--
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2.17.0
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