* FAILED: patch "[PATCH] proc/vmcore: fix clearing user buffer by properly using" failed to apply to 5.10-stable tree
@ 2021-11-22 12:27 gregkh
[not found] ` <CALu+AoRMcX9Xg97yBzHd1qYONNutoX9R+VksxpE0Hr6eUtXPGw@mail.gmail.com>
2021-11-24 20:45 ` [PATCH for 5.10-stable] proc/vmcore: fix clearing user buffer by properly using clear_user() David Hildenbrand
0 siblings, 2 replies; 3+ messages in thread
From: gregkh @ 2021-11-22 12:27 UTC (permalink / raw)
To: david, akpm, bhe, dyoung, prudo, stable, torvalds, vgoyal; +Cc: stable
The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From c1e63117711977cc4295b2ce73de29dd17066c82 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Fri, 19 Nov 2021 16:43:58 -0800
Subject: [PATCH] proc/vmcore: fix clearing user buffer by properly using
clear_user()
To clear a user buffer we cannot simply use memset, we have to use
clear_user(). With a virtio-mem device that registers a vmcore_cb and
has some logically unplugged memory inside an added Linux memory block,
I can easily trigger a BUG by copying the vmcore via "cp":
systemd[1]: Starting Kdump Vmcore Save Service...
kdump[420]: Kdump is using the default log level(3).
kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/
kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/
kdump[465]: saving vmcore-dmesg.txt complete
kdump[467]: saving vmcore
BUG: unable to handle page fault for address: 00007f2374e01000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867
Oops: 0003 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014
RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86
Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81
RSP: 0018:ffffc9000073be08 EFLAGS: 00010212
RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000
RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008
RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50
R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000
R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8
FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0
Call Trace:
read_vmcore+0x236/0x2c0
proc_reg_read+0x55/0xa0
vfs_read+0x95/0x190
ksys_read+0x4f/0xc0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access
Prevention (SMAP)", which is used to detect wrong access from the kernel
to user buffers like this: SMAP triggers a permissions violation on
wrong access. In the x86-64 variant of clear_user(), SMAP is properly
handled via clac()+stac().
To fix, properly use clear_user() when we're dealing with a user buffer.
Link: https://lkml.kernel.org/r/20211112092750.6921-1-david@redhat.com
Fixes: 997c136f518c ("fs/proc/vmcore.c: add hook to read_from_oldmem() to check for non-ram pages")
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Philipp Rudo <prudo@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 30a3b66f475a..509f85148fee 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -154,9 +154,13 @@ ssize_t read_from_oldmem(char *buf, size_t count,
nr_bytes = count;
/* If pfn is not ram, return zeros for sparse dump files */
- if (!pfn_is_ram(pfn))
- memset(buf, 0, nr_bytes);
- else {
+ if (!pfn_is_ram(pfn)) {
+ tmp = 0;
+ if (!userbuf)
+ memset(buf, 0, nr_bytes);
+ else if (clear_user(buf, nr_bytes))
+ tmp = -EFAULT;
+ } else {
if (encrypted)
tmp = copy_oldmem_page_encrypted(pfn, buf,
nr_bytes,
@@ -165,12 +169,12 @@ ssize_t read_from_oldmem(char *buf, size_t count,
else
tmp = copy_oldmem_page(pfn, buf, nr_bytes,
offset, userbuf);
-
- if (tmp < 0) {
- up_read(&vmcore_cb_rwsem);
- return tmp;
- }
}
+ if (tmp < 0) {
+ up_read(&vmcore_cb_rwsem);
+ return tmp;
+ }
+
*ppos += nr_bytes;
count -= nr_bytes;
buf += nr_bytes;
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: FAILED: patch "[PATCH] proc/vmcore: fix clearing user buffer by properly using" failed to apply to 5.10-stable tree
[not found] ` <CALu+AoRMcX9Xg97yBzHd1qYONNutoX9R+VksxpE0Hr6eUtXPGw@mail.gmail.com>
@ 2021-11-23 10:39 ` David Hildenbrand
0 siblings, 0 replies; 3+ messages in thread
From: David Hildenbrand @ 2021-11-23 10:39 UTC (permalink / raw)
To: Dave Young, gregkh
Cc: akpm, bhe, Philipp Rudo, stable, torvalds, Goyal, Vivek
On 23.11.21 07:20, Dave Young wrote:
>
>
> On Mon, 22 Nov 2021 at 20:33, <gregkh@linuxfoundation.org
> <mailto:gregkh@linuxfoundation.org>> wrote:
>
>
> The patch below does not apply to the 5.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org <mailto:stable@vger.kernel.org>>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From c1e63117711977cc4295b2ce73de29dd17066c82 Mon Sep 17 00:00:00 2001
> From: David Hildenbrand <david@redhat.com <mailto:david@redhat.com>>
> Date: Fri, 19 Nov 2021 16:43:58 -0800
> Subject: [PATCH] proc/vmcore: fix clearing user buffer by properly using
> clear_user()
>
>
> I think this is a very corner case and a good-to-have fix in stable,
> but we can also leave it as is.
> I would like to leave this to David. David? Would you like to rebase
> or drop it?
I'll have a look how easy (and different) the backports for the stable
trees area. I assume they are easy, then I'll just do the backport.
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH for 5.10-stable] proc/vmcore: fix clearing user buffer by properly using clear_user()
2021-11-22 12:27 FAILED: patch "[PATCH] proc/vmcore: fix clearing user buffer by properly using" failed to apply to 5.10-stable tree gregkh
[not found] ` <CALu+AoRMcX9Xg97yBzHd1qYONNutoX9R+VksxpE0Hr6eUtXPGw@mail.gmail.com>
@ 2021-11-24 20:45 ` David Hildenbrand
1 sibling, 0 replies; 3+ messages in thread
From: David Hildenbrand @ 2021-11-24 20:45 UTC (permalink / raw)
To: stable
Cc: linux-kernel, gregkh, akpm, David Hildenbrand, Baoquan He,
Dave Young, Vivek Goyal, Philipp Rudo
commit c1e63117711977cc4295b2ce73de29dd17066c82 upstream.
To clear a user buffer we cannot simply use memset, we have to use
clear_user(). With a virtio-mem device that registers a vmcore_cb and
has some logically unplugged memory inside an added Linux memory block,
I can easily trigger a BUG by copying the vmcore via "cp":
systemd[1]: Starting Kdump Vmcore Save Service...
kdump[420]: Kdump is using the default log level(3).
kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/
kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/
kdump[465]: saving vmcore-dmesg.txt complete
kdump[467]: saving vmcore
BUG: unable to handle page fault for address: 00007f2374e01000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867
Oops: 0003 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014
RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86
Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81
RSP: 0018:ffffc9000073be08 EFLAGS: 00010212
RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000
RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008
RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50
R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000
R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8
FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0
Call Trace:
read_vmcore+0x236/0x2c0
proc_reg_read+0x55/0xa0
vfs_read+0x95/0x190
ksys_read+0x4f/0xc0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access
Prevention (SMAP)", which is used to detect wrong access from the kernel
to user buffers like this: SMAP triggers a permissions violation on
wrong access. In the x86-64 variant of clear_user(), SMAP is properly
handled via clac()+stac().
To fix, properly use clear_user() when we're dealing with a user buffer.
Link: https://lkml.kernel.org/r/20211112092750.6921-1-david@redhat.com
Fixes: 997c136f518c ("fs/proc/vmcore.c: add hook to read_from_oldmem() to check for non-ram pages")
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Philipp Rudo <prudo@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
fs/proc/vmcore.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index c3a345c28a93..0e4278d4a769 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -124,9 +124,13 @@ ssize_t read_from_oldmem(char *buf, size_t count,
nr_bytes = count;
/* If pfn is not ram, return zeros for sparse dump files */
- if (pfn_is_ram(pfn) == 0)
- memset(buf, 0, nr_bytes);
- else {
+ if (pfn_is_ram(pfn) == 0) {
+ tmp = 0;
+ if (!userbuf)
+ memset(buf, 0, nr_bytes);
+ else if (clear_user(buf, nr_bytes))
+ tmp = -EFAULT;
+ } else {
if (encrypted)
tmp = copy_oldmem_page_encrypted(pfn, buf,
nr_bytes,
@@ -135,10 +139,10 @@ ssize_t read_from_oldmem(char *buf, size_t count,
else
tmp = copy_oldmem_page(pfn, buf, nr_bytes,
offset, userbuf);
-
- if (tmp < 0)
- return tmp;
}
+ if (tmp < 0)
+ return tmp;
+
*ppos += nr_bytes;
count -= nr_bytes;
buf += nr_bytes;
--
2.31.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2021-11-22 12:27 FAILED: patch "[PATCH] proc/vmcore: fix clearing user buffer by properly using" failed to apply to 5.10-stable tree gregkh
[not found] ` <CALu+AoRMcX9Xg97yBzHd1qYONNutoX9R+VksxpE0Hr6eUtXPGw@mail.gmail.com>
2021-11-23 10:39 ` David Hildenbrand
2021-11-24 20:45 ` [PATCH for 5.10-stable] proc/vmcore: fix clearing user buffer by properly using clear_user() David Hildenbrand
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