The patch titled
Subject: Squashfs: fix uninit-value in squashfs_get_parent
has been added to the -mm mm-nonmm-unstable branch. Its filename is
squashfs-fix-uninit-value-in-squashfs_get_parent.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Phillip Lougher <phillip(a)squashfs.org.uk>
Subject: Squashfs: fix uninit-value in squashfs_get_parent
Date: Fri, 19 Sep 2025 00:33:08 +0100
Syzkaller reports a "KMSAN: uninit-value in squashfs_get_parent" bug.
This is caused by open_by_handle_at() being called with a file handle
containing an invalid parent inode number. In particular the inode number
is that of a symbolic link, rather than a directory.
Squashfs_get_parent() gets called with that symbolic link inode, and
accesses the parent member field.
unsigned int parent_ino = squashfs_i(inode)->parent;
Because non-directory inodes in Squashfs do not have a parent value, this
is uninitialised, and this causes an uninitialised value access.
The fix is to initialise parent with the invalid inode 0, which will cause
an EINVAL error to be returned.
Regular inodes used to share the parent field with the block_list_start
field. This is removed in this commit to enable the parent field to
contain the invalid inode number 0.
Link: https://lkml.kernel.org/r/20250918233308.293861-1-phillip@squashfs.org.uk
Fixes: 122601408d20 ("Squashfs: export operations")
Signed-off-by: Phillip Lougher <phillip(a)squashfs.org.uk>
Reported-by: syzbot+157bdef5cf596ad0da2c(a)syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68cc2431.050a0220.139b6.0001.GAE@google.com/
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/squashfs/inode.c | 7 +++++++
fs/squashfs/squashfs_fs_i.h | 2 +-
2 files changed, 8 insertions(+), 1 deletion(-)
--- a/fs/squashfs/inode.c~squashfs-fix-uninit-value-in-squashfs_get_parent
+++ a/fs/squashfs/inode.c
@@ -169,6 +169,7 @@ int squashfs_read_inode(struct inode *in
squashfs_i(inode)->start = le32_to_cpu(sqsh_ino->start_block);
squashfs_i(inode)->block_list_start = block;
squashfs_i(inode)->offset = offset;
+ squashfs_i(inode)->parent = 0;
inode->i_data.a_ops = &squashfs_aops;
TRACE("File inode %x:%x, start_block %llx, block_list_start "
@@ -216,6 +217,7 @@ int squashfs_read_inode(struct inode *in
squashfs_i(inode)->start = le64_to_cpu(sqsh_ino->start_block);
squashfs_i(inode)->block_list_start = block;
squashfs_i(inode)->offset = offset;
+ squashfs_i(inode)->parent = 0;
inode->i_data.a_ops = &squashfs_aops;
TRACE("File inode %x:%x, start_block %llx, block_list_start "
@@ -296,6 +298,7 @@ int squashfs_read_inode(struct inode *in
inode->i_mode |= S_IFLNK;
squashfs_i(inode)->start = block;
squashfs_i(inode)->offset = offset;
+ squashfs_i(inode)->parent = 0;
if (type == SQUASHFS_LSYMLINK_TYPE) {
__le32 xattr;
@@ -333,6 +336,7 @@ int squashfs_read_inode(struct inode *in
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
rdev = le32_to_cpu(sqsh_ino->rdev);
init_special_inode(inode, inode->i_mode, new_decode_dev(rdev));
+ squashfs_i(inode)->parent = 0;
TRACE("Device inode %x:%x, rdev %x\n",
SQUASHFS_INODE_BLK(ino), offset, rdev);
@@ -357,6 +361,7 @@ int squashfs_read_inode(struct inode *in
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
rdev = le32_to_cpu(sqsh_ino->rdev);
init_special_inode(inode, inode->i_mode, new_decode_dev(rdev));
+ squashfs_i(inode)->parent = 0;
TRACE("Device inode %x:%x, rdev %x\n",
SQUASHFS_INODE_BLK(ino), offset, rdev);
@@ -377,6 +382,7 @@ int squashfs_read_inode(struct inode *in
inode->i_mode |= S_IFSOCK;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
init_special_inode(inode, inode->i_mode, 0);
+ squashfs_i(inode)->parent = 0;
break;
}
case SQUASHFS_LFIFO_TYPE:
@@ -396,6 +402,7 @@ int squashfs_read_inode(struct inode *in
inode->i_op = &squashfs_inode_ops;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
init_special_inode(inode, inode->i_mode, 0);
+ squashfs_i(inode)->parent = 0;
break;
}
default:
--- a/fs/squashfs/squashfs_fs_i.h~squashfs-fix-uninit-value-in-squashfs_get_parent
+++ a/fs/squashfs/squashfs_fs_i.h
@@ -16,6 +16,7 @@ struct squashfs_inode_info {
u64 xattr;
unsigned int xattr_size;
int xattr_count;
+ int parent;
union {
struct {
u64 fragment_block;
@@ -27,7 +28,6 @@ struct squashfs_inode_info {
u64 dir_idx_start;
int dir_idx_offset;
int dir_idx_cnt;
- int parent;
};
};
struct inode vfs_inode;
_
Patches currently in -mm which might be from phillip(a)squashfs.org.uk are
squashfs-fix-uninit-value-in-squashfs_get_parent.patch
The patch titled
Subject: fs/proc/task_mmu: check cur_buf for NULL
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
fs-proc-task_mmu-check-cur_buf-for-null.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Jakub Acs <acsjakub(a)amazon.de>
Subject: fs/proc/task_mmu: check cur_buf for NULL
Date: Fri, 19 Sep 2025 14:21:04 +0000
When the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reaches
pagemap_scan_backout_range(), kernel panics with null-ptr-deref:
[ 44.936808] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI
[ 44.937797] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
[ 44.938391] CPU: 1 UID: 0 PID: 2480 Comm: reproducer Not tainted 6.17.0-rc6 #22 PREEMPT(none)
[ 44.939062] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 44.939935] RIP: 0010:pagemap_scan_thp_entry.isra.0+0x741/0xa80
<snip registers, unreliable trace>
[ 44.946828] Call Trace:
[ 44.947030] <TASK>
[ 44.949219] pagemap_scan_pmd_entry+0xec/0xfa0
[ 44.952593] walk_pmd_range.isra.0+0x302/0x910
[ 44.954069] walk_pud_range.isra.0+0x419/0x790
[ 44.954427] walk_p4d_range+0x41e/0x620
[ 44.954743] walk_pgd_range+0x31e/0x630
[ 44.955057] __walk_page_range+0x160/0x670
[ 44.956883] walk_page_range_mm+0x408/0x980
[ 44.958677] walk_page_range+0x66/0x90
[ 44.958984] do_pagemap_scan+0x28d/0x9c0
[ 44.961833] do_pagemap_cmd+0x59/0x80
[ 44.962484] __x64_sys_ioctl+0x18d/0x210
[ 44.962804] do_syscall_64+0x5b/0x290
[ 44.963111] entry_SYSCALL_64_after_hwframe+0x76/0x7e
vec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers are
allocated and p->vec_buf remains set to NULL.
This breaks an assumption made later in pagemap_scan_backout_range(), that
page_region is always allocated for p->vec_buf_index.
Fix it by explicitly checking cur_buf for NULL before dereferencing.
Other sites that might run into same deref-issue are already (directly or
transitively) protected by checking p->vec_buf.
Note:
From PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output
is requested and it's only the side effects caller is interested in, hence
it passes check in pagemap_scan_get_args().
This issue was found by syzkaller.
Link: https://lkml.kernel.org/r/20250919142106.43527-1-acsjakub@amazon.de
Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
Signed-off-by: Jakub Acs <acsjakub(a)amazon.de>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Jinjiang Tu <tujinjiang(a)huawei.com>
Cc: Suren Baghdasaryan <surenb(a)google.com>
Cc: Penglei Jiang <superman.xpt(a)gmail.com>
Cc: Mark Brown <broonie(a)kernel.org>
Cc: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: Ryan Roberts <ryan.roberts(a)arm.com>
Cc: Andrei Vagin <avagin(a)gmail.com>
Cc: "Micha�� Miros��aw" <mirq-linux(a)rere.qmqm.pl>
Cc: Stephen Rothwell <sfr(a)canb.auug.org.au>
Cc: Muhammad Usama Anjum <usama.anjum(a)collabora.com>
Cc: Alexey Dobriyan <adobriyan(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/proc/task_mmu.c | 3 +++
1 file changed, 3 insertions(+)
--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-check-cur_buf-for-null
+++ a/fs/proc/task_mmu.c
@@ -2417,6 +2417,9 @@ static void pagemap_scan_backout_range(s
{
struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];
+ if (!cur_buf)
+ return;
+
if (cur_buf->start != addr)
cur_buf->end = addr;
else
_
Patches currently in -mm which might be from acsjakub(a)amazon.de are
fs-proc-task_mmu-check-cur_buf-for-null.patch
Bug-report: https://lore.kernel.org/all/915c0e00-b92d-4e37-9d4b-0f6a4580da97@oracle.com/
Summary: While backporting commit: 7c62c442b6eb ("x86/vmscape: Enumerate
VMSCAPE bug") to 6.12.y --> VULNBL_AMD(0x1a, SRSO | VMSCAPE) was added
even when 6.12.y doesn't have commit: 877818802c3e ("x86/bugs: Add
SRSO_USER_KERNEL_NO support").
Boris Ostrovsky suggested backporting three commits to 6.12.y:
1. commit: 877818802c3e ("x86/bugs: Add SRSO_USER_KERNEL_NO support")
2. commit: 8442df2b49ed ("x86/bugs: KVM: Add support for SRSO_MSR_FIX")
and its fix
3. commit: e3417ab75ab2 ("KVM: SVM: Set/clear SRSO's BP_SPEC_REDUCE on 0
<=> 1 VM count transitions") -- Maybe optional
Which changes current mitigation status on turin for 6.12.48 from Safe
RET to Reduced Speculation, leaving it with Safe RET liely causes heavy
performance regressions.
This three patches together change mitigation status from Safe RET to
Reduced Speculation
Tested on Turin:
[ 3.188134] Speculative Return Stack Overflow: Mitigation: Reduced Speculation
Backports:
1. Patch 1 had minor conflict as VMSCAPE commit added VULNBL_AMD(0x1a,
SRSO | VMSCAPE), and resolution is to skip that line.
2. Patch 2 and 3 are clean cherry-picks, 3 is a fix for 2.
Note: I verified if this problem is also on other stable trees like (6.6
--> 5.10, no they don't have this backport problem)
Thanks,
Harshit
Borislav Petkov (1):
x86/bugs: KVM: Add support for SRSO_MSR_FIX
Borislav Petkov (AMD) (1):
x86/bugs: Add SRSO_USER_KERNEL_NO support
Sean Christopherson (1):
KVM: SVM: Set/clear SRSO's BP_SPEC_REDUCE on 0 <=> 1 VM count
transitions
Documentation/admin-guide/hw-vuln/srso.rst | 13 +++++
arch/x86/include/asm/cpufeatures.h | 5 ++
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/kernel/cpu/bugs.c | 28 ++++++++--
arch/x86/kvm/svm/svm.c | 65 ++++++++++++++++++++++
arch/x86/kvm/svm/svm.h | 2 +
arch/x86/lib/msr.c | 2 +
7 files changed, 112 insertions(+), 4 deletions(-)
--
2.50.1
The following commit has been merged into the x86/cpu branch of tip:
Commit-ID: 32278c677947ae2f042c9535674a7fff9a245dd3
Gitweb: https://git.kernel.org/tip/32278c677947ae2f042c9535674a7fff9a245dd3
Author: Sean Christopherson <seanjc(a)google.com>
AuthorDate: Fri, 08 Aug 2025 10:23:56 -07:00
Committer: Borislav Petkov (AMD) <bp(a)alien8.de>
CommitterDate: Fri, 19 Sep 2025 20:21:12 +02:00
x86/umip: Check that the instruction opcode is at least two bytes
When checking for a potential UMIP violation on #GP, verify the decoder found
at least two opcode bytes to avoid false positives when the kernel encounters
an unknown instruction that starts with 0f. Because the array of opcode.bytes
is zero-initialized by insn_init(), peeking at bytes[1] will misinterpret
garbage as a potential SLDT or STR instruction, and can incorrectly trigger
emulation.
E.g. if a VPALIGNR instruction
62 83 c5 05 0f 08 ff vpalignr xmm17{k5},xmm23,XMMWORD PTR [r8],0xff
hits a #GP, the kernel emulates it as STR and squashes the #GP (and corrupts
the userspace code stream).
Arguably the check should look for exactly two bytes, but no three byte
opcodes use '0f 00 xx' or '0f 01 xx' as an escape, i.e. it should be
impossible to get a false positive if the first two opcode bytes match '0f 00'
or '0f 01'. Go with a more conservative check with respect to the existing
code to minimize the chances of breaking userspace, e.g. due to decoder
weirdness.
Analyzed by Nick Bray <ncbray(a)google.com>.
Fixes: 1e5db223696a ("x86/umip: Add emulation code for UMIP instructions")
Reported-by: Dan Snyder <dansnyder(a)google.com>
Signed-off-by: Sean Christopherson <seanjc(a)google.com>
Signed-off-by: Borislav Petkov (AMD) <bp(a)alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz(a)infradead.org>
Cc: stable(a)vger.kernel.org
---
arch/x86/kernel/umip.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 5a4b213..406ac01 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -156,8 +156,8 @@ static int identify_insn(struct insn *insn)
if (!insn->modrm.nbytes)
return -EINVAL;
- /* All the instructions of interest start with 0x0f. */
- if (insn->opcode.bytes[0] != 0xf)
+ /* The instructions of interest have 2-byte opcodes: 0F 00 or 0F 01. */
+ if (insn->opcode.nbytes < 2 || insn->opcode.bytes[0] != 0xf)
return -EINVAL;
if (insn->opcode.bytes[1] == 0x1) {
The following commit has been merged into the x86/cpu branch of tip:
Commit-ID: 27b1fd62012dfe9d3eb8ecde344d7aa673695ecf
Gitweb: https://git.kernel.org/tip/27b1fd62012dfe9d3eb8ecde344d7aa673695ecf
Author: Sean Christopherson <seanjc(a)google.com>
AuthorDate: Fri, 08 Aug 2025 10:23:57 -07:00
Committer: Borislav Petkov (AMD) <bp(a)alien8.de>
CommitterDate: Fri, 19 Sep 2025 21:34:48 +02:00
x86/umip: Fix decoding of register forms of 0F 01 (SGDT and SIDT aliases)
Filter out the register forms of 0F 01 when determining whether or not to
emulate in response to a potential UMIP violation #GP, as SGDT and SIDT only
accept memory operands. The register variants of 0F 01 are used to encode
instructions for things like VMX and SGX, i.e. not checking the Mod field
would cause the kernel to incorrectly emulate on #GP, e.g. due to a CPL
violation on VMLAUNCH.
Fixes: 1e5db223696a ("x86/umip: Add emulation code for UMIP instructions")
Signed-off-by: Sean Christopherson <seanjc(a)google.com>
Signed-off-by: Borislav Petkov (AMD) <bp(a)alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz(a)infradead.org>
Cc: stable(a)vger.kernel.org
---
arch/x86/kernel/umip.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 406ac01..d432f38 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -163,8 +163,19 @@ static int identify_insn(struct insn *insn)
if (insn->opcode.bytes[1] == 0x1) {
switch (X86_MODRM_REG(insn->modrm.value)) {
case 0:
+ /* The reg form of 0F 01 /0 encodes VMX instructions. */
+ if (X86_MODRM_MOD(insn->modrm.value) == 3)
+ return -EINVAL;
+
return UMIP_INST_SGDT;
case 1:
+ /*
+ * The reg form of 0F 01 /1 encodes MONITOR/MWAIT,
+ * STAC/CLAC, and ENCLS.
+ */
+ if (X86_MODRM_MOD(insn->modrm.value) == 3)
+ return -EINVAL;
+
return UMIP_INST_SIDT;
case 4:
return UMIP_INST_SMSW;
From: HariKrishna Sagala <hariconscious(a)gmail.com>
Syzbot reported an uninit-value bug on at kmalloc_reserve for
commit 320475fbd590 ("Merge tag 'mtd/fixes-for-6.17-rc6' of
git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux")'
Syzbot KMSAN reported use of uninitialized memory originating from functions
"kmalloc_reserve()", where memory allocated via "kmem_cache_alloc_node()" or
"kmalloc_node_track_caller()" was not explicitly initialized.
This can lead to undefined behavior when the allocated buffer
is later accessed.
Fix this by requesting the initialized memory using the gfp flag
appended with the option "__GFP_ZERO".
Reported-by: syzbot+9a4fbb77c9d4aacd3388(a)syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
Fixes: 915d975b2ffa ("net: deal with integer overflows in
kmalloc_reserve()")
Tested-by: syzbot+9a4fbb77c9d4aacd3388(a)syzkaller.appspotmail.com
Signed-off-by: HariKrishna Sagala <hariconscious(a)gmail.com>
---
net/core/skbuff.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ee0274417948..2308ebf99bbd 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -573,6 +573,7 @@ static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
void *obj;
obj_size = SKB_HEAD_ALIGN(*size);
+ flags |= __GFP_ZERO;
if (obj_size <= SKB_SMALL_HEAD_CACHE_SIZE &&
!(flags & KMALLOC_NOT_NORMAL_BITS)) {
obj = kmem_cache_alloc_node(net_hotdata.skb_small_head_cache,
--
2.43.0
Once of_device_register() failed, we should call put_device() to
decrement reference count for cleanup. Or it could cause memory leak.
So fix this by calling put_device(), then the name can be freed in
kobject_cleanup().
Calling path: of_device_register() -> of_device_add() -> device_add().
As comment of device_add() says, 'if device_add() succeeds, you should
call device_del() when you want to get rid of it. If device_add() has
not succeeded, use only put_device() to drop the reference count'.
Found by code review.
Cc: stable(a)vger.kernel.org
Fixes: cf44bbc26cf1 ("[SPARC]: Beginnings of generic of_device framework.")
Signed-off-by: Ma Ke <make24(a)iscas.ac.cn>
---
Changes in v2:
- retained kfree() manually due to the lack of a release callback function.
---
arch/sparc/kernel/of_device_64.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/sparc/kernel/of_device_64.c b/arch/sparc/kernel/of_device_64.c
index f98c2901f335..f53092b07b9e 100644
--- a/arch/sparc/kernel/of_device_64.c
+++ b/arch/sparc/kernel/of_device_64.c
@@ -677,6 +677,7 @@ static struct platform_device * __init scan_one_device(struct device_node *dp,
if (of_device_register(op)) {
printk("%pOF: Could not register of device.\n", dp);
+ put_device(&op->dev);
kfree(op);
op = NULL;
}
--
2.25.1
Hi stable maintainers,
While skimming over stable backports for VMSCAPE commits, I found
something unusual.
This is regarding the 6.12.y commit: 7c62c442b6eb ("x86/vmscape:
Enumerate VMSCAPE bug")
commit 7c62c442b6eb95d21bc4c5afc12fee721646ebe2
Author: Pawan Gupta <pawan.kumar.gupta(a)linux.intel.com>
Date: Thu Aug 14 10:20:42 2025 -0700
x86/vmscape: Enumerate VMSCAPE bug
Commit a508cec6e5215a3fbc7e73ae86a5c5602187934d upstream.
The VMSCAPE vulnerability may allow a guest to cause Branch Target
Injection (BTI) in userspace hypervisors.
Kernels (both host and guest) have existing defenses against direct BTI
attacks from guests. There are also inter-process BTI mitigations which
prevent processes from attacking each other. However, the threat in
this
case is to a userspace hypervisor within the same process as the
attacker.
Userspace hypervisors have access to their own sensitive data like disk
encryption keys and also typically have access to all guest data. This
means guest userspace may use the hypervisor as a confused deputy
to attack
sensitive guest kernel data. There are no existing mitigations for
these
attacks.
Introduce X86_BUG_VMSCAPE for this vulnerability and set it on affected
Intel and AMD CPUs.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta(a)linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen(a)linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp(a)alien8.de>
Signed-off-by: Borislav Petkov (AMD) <bp(a)alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
So the problem in this commit is this part of the backport:
in file: arch/x86/kernel/cpu/common.c
VULNBL_AMD(0x15, RETBLEED),
VULNBL_AMD(0x16, RETBLEED),
- VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO),
- VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO),
- VULNBL_AMD(0x19, SRSO | TSA),
+ VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+ VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+ VULNBL_AMD(0x19, SRSO | TSA | VMSCAPE),
+ VULNBL_AMD(0x1a, SRSO | VMSCAPE),
+
{}
Notice the part where VULNBL_AMD(0x1a, SRSO | VMSCAPE) is added, 6.12.y
doesn't have commit: 877818802c3e ("x86/bugs: Add SRSO_USER_KERNEL_NO
support") so I think we shouldn't be adding VULNBL_AMD(0x1a, SRSO |
VMSCAPE) directly.
Boris Ostrovsky suggested me to verify this on a Turin machine as this
could cause a very big performance regression : and stated if SRSO
mitigation status is Safe RET we are likely in a problem, and we are in
that situation.
# lscpu | grep -E "CPU family"
CPU family: 26
Notes: CPU ID 26 -> 0x1a
And Turin machine reports the SRSO mitigation status as "Safe RET"
# uname -r
6.12.48-master.20250917.el8.rc1.x86_64
# cat /sys/devices/system/cpu/vulnerabilities/spec_rstack_overflow
Mitigation: Safe RET
Boris Ostrovsky suggested backporting three commits to 6.12.y:
1. commit: 877818802c3e ("x86/bugs: Add SRSO_USER_KERNEL_NO support")
2. commit: 8442df2b49ed ("x86/bugs: KVM: Add support for SRSO_MSR_FIX")
and its fix
3. commit: e3417ab75ab2 ("KVM: SVM: Set/clear SRSO's BP_SPEC_REDUCE on 0
<=> 1 VM count transitions") -- Maybe optional
After backporting these three:
# uname -r
6.12.48-master.20250919.el8.dev.x86_64 // Note this this is kernel with
patches above three applied.
# dmesg | grep -C 2 Reduce
[ 3.186135] Speculative Store Bypass: Mitigation: Speculative Store
Bypass disabled via prctl
[ 3.187135] Speculative Return Stack Overflow: Reducing speculation to
address VM/HV SRSO attack vector.
[ 3.188134] Speculative Return Stack Overflow: Mitigation: Reduced
Speculation
[ 3.189135] VMSCAPE: Mitigation: IBPB before exit to userspace
[ 3.191139] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point
registers'
# cat /sys/devices/system/cpu/vulnerabilities/spec_rstack_overflow
Mitigation: Reduced Speculation
I can send my backports to stable if this looks good. Thoughts ?
Thanks,
Harshit