On 11 Oct 2022, it was reported that the crc32 verification
of the u-boot environment failed only on big-endian systems
for the u-boot-env nvmem layout driver with the following error.
Invalid calculated CRC32: 0x88cd6f09 (expected: 0x096fcd88)
This problem has been present since the driver was introduced,
and before it was made into a layout driver.
The suggested fix at the time was to use further endianness
conversion macros in order to have both the stored and calculated
crc32 values to compare always represented in the system's endianness.
This was not accepted due to sparse warnings
and some disagreement on how to handle the situation.
Later on in a newer revision of the patch, it was proposed to use
cpu_to_le32() for both values to compare instead of le32_to_cpu()
and store the values as __le32 type to remove compilation errors.
The necessity of this is based on the assumption that the use of crc32()
requires endianness conversion because the algorithm uses little-endian,
however, this does not prove to be the case and the issue is unrelated.
Upon inspecting the current kernel code,
there already is an existing use of le32_to_cpu() in this driver,
which suggests there already is special handling for big-endian systems,
however, it is big-endian systems that have the problem.
This, being the only functional difference between architectures
in the driver combined with the fact that the suggested fix
was to use the exact same endianness conversion for the values
brings up the possibility that it was not necessary to begin with,
as the same endianness conversion for two values expected to be the same
is expected to be equivalent to no conversion at all.
After inspecting the u-boot environment of devices of both endianness
and trying to remove the existing endianness conversion,
the problem is resolved in an equivalent way as the other suggested fixes.
Ultimately, it seems that u-boot is agnostic to endianness
at least for the purpose of environment variables.
In other words, u-boot reads and writes the stored crc32 value
with the same endianness that the crc32 value is calculated with
in whichever endianness a certain architecture runs on.
Therefore, the u-boot-env driver does not need to convert endianness.
Remove the usage of endianness macros in the u-boot-env driver,
and change the type of local variables to maintain the same return type.
If there is a special situation in the case of endianness,
it would be a corner case and should be handled by a unique "compatible".
Even though it is not necessary to use endianness conversion macros here,
it may be useful to use them in the future for consistent error printing.
Fixes: d5542923f200 ("nvmem: add driver handling U-Boot environment variables")
Reported-by: INAGAKI Hiroshi <musashino.open(a)gmail.com>
Link: https://lore.kernel.org/all/20221011024928.1807-1-musashino.open@gmail.com
Cc: <stable(a)vger.kernel.org> # 6.12.x
Cc: <stable(a)vger.kernel.org> # 6.6.x: f4cf4e5: Revert "nvmem: add new config option"
Cc: <stable(a)vger.kernel.org> # 6.6.x: 7f38b70: of: device: Export of_device_make_bus_id()
Cc: <stable(a)vger.kernel.org> # 6.6.x: 4a1a402: nvmem: Move of_nvmem_layout_get_container() in another header
Cc: <stable(a)vger.kernel.org> # 6.6.x: fc29fd8: nvmem: core: Rework layouts to become regular devices
Cc: <stable(a)vger.kernel.org> # 6.6.x: 0331c61: nvmem: core: Expose cells through sysfs
Cc: <stable(a)vger.kernel.org> # 6.6.x: 401df0d: nvmem: layouts: refactor .add_cells() callback arguments
Cc: <stable(a)vger.kernel.org> # 6.6.x: 6d0ca4a: nvmem: layouts: store owner from modules with nvmem_layout_driver_register()
Cc: <stable(a)vger.kernel.org> # 6.6.x: 5f15811: nvmem: layouts: add U-Boot env layout
Cc: <stable(a)vger.kernel.org> # 6.6.x
Signed-off-by: Michael C. Pratt <mcpratt(a)pm.me>
---
drivers/nvmem/layouts/u-boot-env.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/nvmem/layouts/u-boot-env.c b/drivers/nvmem/layouts/u-boot-env.c
index 731e6f4f12b2..21f6dcf905dd 100644
--- a/drivers/nvmem/layouts/u-boot-env.c
+++ b/drivers/nvmem/layouts/u-boot-env.c
@@ -92,7 +92,7 @@ int u_boot_env_parse(struct device *dev, struct nvmem_device *nvmem,
size_t crc32_data_offset;
size_t crc32_data_len;
size_t crc32_offset;
- __le32 *crc32_addr;
+ uint32_t *crc32_addr;
size_t data_offset;
size_t data_len;
size_t dev_size;
@@ -143,8 +143,8 @@ int u_boot_env_parse(struct device *dev, struct nvmem_device *nvmem,
goto err_kfree;
}
- crc32_addr = (__le32 *)(buf + crc32_offset);
- crc32 = le32_to_cpu(*crc32_addr);
+ crc32_addr = (uint32_t *)(buf + crc32_offset);
+ crc32 = *crc32_addr;
crc32_data_len = dev_size - crc32_data_offset;
data_len = dev_size - data_offset;
base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557
--
2.30.2
For some odd reason 5.10 kernel series doesn't compile with a newer
toolchain since 2025-02-09:
2025-02-09T17:32:07.7991299Z GEN .version
2025-02-09T17:32:07.8270062Z CHK include/generated/compile.h
2025-02-09T17:32:07.8540777Z LD vmlinux.o
2025-02-09T17:32:11.7210899Z MODPOST vmlinux.symvers
2025-02-09T17:32:12.0869599Z MODINFO modules.builtin.modinfo
2025-02-09T17:32:12.1403022Z GEN modules.builtin
2025-02-09T17:32:12.1475659Z LD .tmp_vmlinux.btf
2025-02-09T17:32:19.6117204Z BTF .btf.vmlinux.bin.o
2025-02-09T17:32:31.2916650Z LD .tmp_vmlinux.kallsyms1
2025-02-09T17:32:34.8731104Z KSYMS .tmp_vmlinux.kallsyms1.S
2025-02-09T17:32:35.4910608Z AS .tmp_vmlinux.kallsyms1.o
2025-02-09T17:32:35.9662538Z LD .tmp_vmlinux.kallsyms2
2025-02-09T17:32:39.2595984Z KSYMS .tmp_vmlinux.kallsyms2.S
2025-02-09T17:32:39.8802028Z AS .tmp_vmlinux.kallsyms2.o
2025-02-09T17:32:40.3659440Z LD vmlinux
2025-02-09T17:32:48.0031558Z BTFIDS vmlinux
2025-02-09T17:32:48.0143553Z FAILED unresolved symbol filp_close
2025-02-09T17:32:48.5019928Z make: *** [Makefile:1207: vmlinux] Error 255
2025-02-09T17:32:48.5061241Z ==> ERROR: A failure occurred in build().
5.10.234 built fine couple of days ago with the older one. There were
slight changes made. 5.4 and 5.15 still compile.
Wonder what might be missing here ...
--
Best, Philip
The patch below does not apply to the 6.6-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(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 358de8b4f201bc05712484b15f0109b1ae3516a8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024021932-lavish-expel-58e5@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
358de8b4f201 ("kbuild: rpm-pkg: simplify installkernel %post")
0df8e9708594 ("scripts: clean up IA-64 code")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 358de8b4f201bc05712484b15f0109b1ae3516a8 Mon Sep 17 00:00:00 2001
From: Jose Ignacio Tornos Martinez <jtornosm(a)redhat.com>
Date: Mon, 29 Jan 2024 10:28:19 +0100
Subject: [PATCH] kbuild: rpm-pkg: simplify installkernel %post
The new installkernel application that is now included in systemd-udev
package allows installation although destination files are already present
in the boot directory of the kernel package, but is failing with the
implemented workaround for the old installkernel application from grubby
package.
For the new installkernel application, as Davide says:
<<The %post currently does a shuffling dance before calling installkernel.
This isn't actually necessary afaict, and the current implementation
ends up triggering downstream issues such as
https://github.com/systemd/systemd/issues/29568
This commit simplifies the logic to remove the shuffling. For reference,
the original logic was added in commit 3c9c7a14b627("rpm-pkg: add %post
section to create initramfs and grub hooks").>>
But we need to keep the old behavior as well, because the old installkernel
application from grubby package, does not allow this simplification and
we need to be backward compatible to avoid issues with the different
packages.
Mimic Fedora shipping process and store vmlinuz, config amd System.map
in the module directory instead of the boot directory. In this way, we will
avoid the commented problem for all the cases, because the new destination
files are not going to exist in the boot directory of the kernel package.
Replace installkernel tool with kernel-install tool, because the latter is
more complete.
Besides, after installkernel tool execution, check to complete if the
correct package files vmlinuz, System.map and config files are present
in /boot directory, and if necessary, copy manually for install operation.
In this way, take into account if files were not previously copied from
/usr/lib/kernel/install.d/* scripts and if the suitable files for the
requested package are present (it could be others if the rpm files were
replace with a new pacakge with the same release and a different build).
Tested with Fedora 38, Fedora 39, RHEL 9, Oracle Linux 9.3,
openSUSE Tumbleweed and openMandrive ROME, using dnf/zypper and rpm tools.
cc: stable(a)vger.kernel.org
Co-Developed-by: Davide Cavalca <dcavalca(a)meta.com>
Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm(a)redhat.com>
Signed-off-by: Masahiro Yamada <masahiroy(a)kernel.org>
diff --git a/scripts/package/kernel.spec b/scripts/package/kernel.spec
index 89298983a169..f58726671fb3 100644
--- a/scripts/package/kernel.spec
+++ b/scripts/package/kernel.spec
@@ -55,12 +55,12 @@ patch -p1 < %{SOURCE2}
%{make} %{makeflags} KERNELRELEASE=%{KERNELRELEASE} KBUILD_BUILD_VERSION=%{release}
%install
-mkdir -p %{buildroot}/boot
-cp $(%{make} %{makeflags} -s image_name) %{buildroot}/boot/vmlinuz-%{KERNELRELEASE}
+mkdir -p %{buildroot}/lib/modules/%{KERNELRELEASE}
+cp $(%{make} %{makeflags} -s image_name) %{buildroot}/lib/modules/%{KERNELRELEASE}/vmlinuz
%{make} %{makeflags} INSTALL_MOD_PATH=%{buildroot} modules_install
%{make} %{makeflags} INSTALL_HDR_PATH=%{buildroot}/usr headers_install
-cp System.map %{buildroot}/boot/System.map-%{KERNELRELEASE}
-cp .config %{buildroot}/boot/config-%{KERNELRELEASE}
+cp System.map %{buildroot}/lib/modules/%{KERNELRELEASE}
+cp .config %{buildroot}/lib/modules/%{KERNELRELEASE}/config
ln -fns /usr/src/kernels/%{KERNELRELEASE} %{buildroot}/lib/modules/%{KERNELRELEASE}/build
%if %{with_devel}
%{make} %{makeflags} run-command KBUILD_RUN_COMMAND='${srctree}/scripts/package/install-extmod-build %{buildroot}/usr/src/kernels/%{KERNELRELEASE}'
@@ -70,13 +70,14 @@ ln -fns /usr/src/kernels/%{KERNELRELEASE} %{buildroot}/lib/modules/%{KERNELRELEA
rm -rf %{buildroot}
%post
-if [ -x /sbin/installkernel -a -r /boot/vmlinuz-%{KERNELRELEASE} -a -r /boot/System.map-%{KERNELRELEASE} ]; then
-cp /boot/vmlinuz-%{KERNELRELEASE} /boot/.vmlinuz-%{KERNELRELEASE}-rpm
-cp /boot/System.map-%{KERNELRELEASE} /boot/.System.map-%{KERNELRELEASE}-rpm
-rm -f /boot/vmlinuz-%{KERNELRELEASE} /boot/System.map-%{KERNELRELEASE}
-/sbin/installkernel %{KERNELRELEASE} /boot/.vmlinuz-%{KERNELRELEASE}-rpm /boot/.System.map-%{KERNELRELEASE}-rpm
-rm -f /boot/.vmlinuz-%{KERNELRELEASE}-rpm /boot/.System.map-%{KERNELRELEASE}-rpm
+if [ -x /usr/bin/kernel-install ]; then
+ /usr/bin/kernel-install add %{KERNELRELEASE} /lib/modules/%{KERNELRELEASE}/vmlinuz
fi
+for file in vmlinuz System.map config; do
+ if ! cmp --silent "/lib/modules/%{KERNELRELEASE}/${file}" "/boot/${file}-%{KERNELRELEASE}"; then
+ cp "/lib/modules/%{KERNELRELEASE}/${file}" "/boot/${file}-%{KERNELRELEASE}"
+ fi
+done
%preun
if [ -x /sbin/new-kernel-pkg ]; then
@@ -94,7 +95,6 @@ fi
%defattr (-, root, root)
/lib/modules/%{KERNELRELEASE}
%exclude /lib/modules/%{KERNELRELEASE}/build
-/boot/*
%files headers
%defattr (-, root, root)
The patch below does not apply to the 6.6-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(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025051202-nutrient-upswing-4a86@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 Mon Sep 17 00:00:00 2001
From: Gavin Guo <gavinguo(a)igalia.com>
Date: Mon, 21 Apr 2025 19:35:36 +0800
Subject: [PATCH] mm/huge_memory: fix dereferencing invalid pmd migration entry
When migrating a THP, concurrent access to the PMD migration entry during
a deferred split scan can lead to an invalid address access, as
illustrated below. To prevent this invalid access, it is necessary to
check the PMD migration entry and return early. In this context, there is
no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the
equality of the target folio. Since the PMD migration entry is locked, it
cannot be served as the target.
Mailing list discussion and explanation from Hugh Dickins: "An anon_vma
lookup points to a location which may contain the folio of interest, but
might instead contain another folio: and weeding out those other folios is
precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of
replacing the wrong folio" comment a few lines above it) is for."
BUG: unable to handle page fault for address: ffffea60001db008
CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60
Call Trace:
<TASK>
try_to_migrate_one+0x28c/0x3730
rmap_walk_anon+0x4f6/0x770
unmap_folio+0x196/0x1f0
split_huge_page_to_list_to_order+0x9f6/0x1560
deferred_split_scan+0xac5/0x12a0
shrinker_debugfs_scan_write+0x376/0x470
full_proxy_write+0x15c/0x220
vfs_write+0x2fc/0xcb0
ksys_write+0x146/0x250
do_syscall_64+0x6a/0x120
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The bug is found by syzkaller on an internal kernel, then confirmed on
upstream.
Link: https://lkml.kernel.org/r/20250421113536.3682201-1-gavinguo@igalia.com
Link: https://lore.kernel.org/all/20250414072737.1698513-1-gavinguo@igalia.com/
Link: https://lore.kernel.org/all/20250418085802.2973519-1-gavinguo@igalia.com/
Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path")
Signed-off-by: Gavin Guo <gavinguo(a)igalia.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Hugh Dickins <hughd(a)google.com>
Acked-by: Zi Yan <ziy(a)nvidia.com>
Reviewed-by: Gavin Shan <gshan(a)redhat.com>
Cc: Florent Revest <revest(a)google.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Miaohe Lin <linmiaohe(a)huawei.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2a47682d1ab7..47d76d03ce30 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3075,6 +3075,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmd, bool freeze, struct folio *folio)
{
+ bool pmd_migration = is_pmd_migration_entry(*pmd);
+
VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
@@ -3085,9 +3087,12 @@ void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
* require a folio to check the PMD against. Otherwise, there
* is a risk of replacing the wrong folio.
*/
- if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
- is_pmd_migration_entry(*pmd)) {
- if (folio && folio != pmd_folio(*pmd))
+ if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || pmd_migration) {
+ /*
+ * Do not apply pmd_folio() to a migration entry; and folio lock
+ * guarantees that it must be of the wrong folio anyway.
+ */
+ if (folio && (pmd_migration || folio != pmd_folio(*pmd)))
return;
__split_huge_pmd_locked(vma, pmd, address, freeze);
}
The patch below does not apply to the 5.15-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(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025051204-tidal-lake-6ae7@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 Mon Sep 17 00:00:00 2001
From: Gavin Guo <gavinguo(a)igalia.com>
Date: Mon, 21 Apr 2025 19:35:36 +0800
Subject: [PATCH] mm/huge_memory: fix dereferencing invalid pmd migration entry
When migrating a THP, concurrent access to the PMD migration entry during
a deferred split scan can lead to an invalid address access, as
illustrated below. To prevent this invalid access, it is necessary to
check the PMD migration entry and return early. In this context, there is
no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the
equality of the target folio. Since the PMD migration entry is locked, it
cannot be served as the target.
Mailing list discussion and explanation from Hugh Dickins: "An anon_vma
lookup points to a location which may contain the folio of interest, but
might instead contain another folio: and weeding out those other folios is
precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of
replacing the wrong folio" comment a few lines above it) is for."
BUG: unable to handle page fault for address: ffffea60001db008
CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60
Call Trace:
<TASK>
try_to_migrate_one+0x28c/0x3730
rmap_walk_anon+0x4f6/0x770
unmap_folio+0x196/0x1f0
split_huge_page_to_list_to_order+0x9f6/0x1560
deferred_split_scan+0xac5/0x12a0
shrinker_debugfs_scan_write+0x376/0x470
full_proxy_write+0x15c/0x220
vfs_write+0x2fc/0xcb0
ksys_write+0x146/0x250
do_syscall_64+0x6a/0x120
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The bug is found by syzkaller on an internal kernel, then confirmed on
upstream.
Link: https://lkml.kernel.org/r/20250421113536.3682201-1-gavinguo@igalia.com
Link: https://lore.kernel.org/all/20250414072737.1698513-1-gavinguo@igalia.com/
Link: https://lore.kernel.org/all/20250418085802.2973519-1-gavinguo@igalia.com/
Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path")
Signed-off-by: Gavin Guo <gavinguo(a)igalia.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Hugh Dickins <hughd(a)google.com>
Acked-by: Zi Yan <ziy(a)nvidia.com>
Reviewed-by: Gavin Shan <gshan(a)redhat.com>
Cc: Florent Revest <revest(a)google.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Miaohe Lin <linmiaohe(a)huawei.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2a47682d1ab7..47d76d03ce30 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3075,6 +3075,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmd, bool freeze, struct folio *folio)
{
+ bool pmd_migration = is_pmd_migration_entry(*pmd);
+
VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
@@ -3085,9 +3087,12 @@ void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
* require a folio to check the PMD against. Otherwise, there
* is a risk of replacing the wrong folio.
*/
- if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
- is_pmd_migration_entry(*pmd)) {
- if (folio && folio != pmd_folio(*pmd))
+ if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || pmd_migration) {
+ /*
+ * Do not apply pmd_folio() to a migration entry; and folio lock
+ * guarantees that it must be of the wrong folio anyway.
+ */
+ if (folio && (pmd_migration || folio != pmd_folio(*pmd)))
return;
__split_huge_pmd_locked(vma, pmd, address, freeze);
}
The patch below does not apply to the 5.4-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(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025051206-t-shirt-wrist-ad33@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 Mon Sep 17 00:00:00 2001
From: Gavin Guo <gavinguo(a)igalia.com>
Date: Mon, 21 Apr 2025 19:35:36 +0800
Subject: [PATCH] mm/huge_memory: fix dereferencing invalid pmd migration entry
When migrating a THP, concurrent access to the PMD migration entry during
a deferred split scan can lead to an invalid address access, as
illustrated below. To prevent this invalid access, it is necessary to
check the PMD migration entry and return early. In this context, there is
no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the
equality of the target folio. Since the PMD migration entry is locked, it
cannot be served as the target.
Mailing list discussion and explanation from Hugh Dickins: "An anon_vma
lookup points to a location which may contain the folio of interest, but
might instead contain another folio: and weeding out those other folios is
precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of
replacing the wrong folio" comment a few lines above it) is for."
BUG: unable to handle page fault for address: ffffea60001db008
CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60
Call Trace:
<TASK>
try_to_migrate_one+0x28c/0x3730
rmap_walk_anon+0x4f6/0x770
unmap_folio+0x196/0x1f0
split_huge_page_to_list_to_order+0x9f6/0x1560
deferred_split_scan+0xac5/0x12a0
shrinker_debugfs_scan_write+0x376/0x470
full_proxy_write+0x15c/0x220
vfs_write+0x2fc/0xcb0
ksys_write+0x146/0x250
do_syscall_64+0x6a/0x120
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The bug is found by syzkaller on an internal kernel, then confirmed on
upstream.
Link: https://lkml.kernel.org/r/20250421113536.3682201-1-gavinguo@igalia.com
Link: https://lore.kernel.org/all/20250414072737.1698513-1-gavinguo@igalia.com/
Link: https://lore.kernel.org/all/20250418085802.2973519-1-gavinguo@igalia.com/
Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path")
Signed-off-by: Gavin Guo <gavinguo(a)igalia.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Hugh Dickins <hughd(a)google.com>
Acked-by: Zi Yan <ziy(a)nvidia.com>
Reviewed-by: Gavin Shan <gshan(a)redhat.com>
Cc: Florent Revest <revest(a)google.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Miaohe Lin <linmiaohe(a)huawei.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2a47682d1ab7..47d76d03ce30 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3075,6 +3075,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmd, bool freeze, struct folio *folio)
{
+ bool pmd_migration = is_pmd_migration_entry(*pmd);
+
VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
@@ -3085,9 +3087,12 @@ void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
* require a folio to check the PMD against. Otherwise, there
* is a risk of replacing the wrong folio.
*/
- if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
- is_pmd_migration_entry(*pmd)) {
- if (folio && folio != pmd_folio(*pmd))
+ if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || pmd_migration) {
+ /*
+ * Do not apply pmd_folio() to a migration entry; and folio lock
+ * guarantees that it must be of the wrong folio anyway.
+ */
+ if (folio && (pmd_migration || folio != pmd_folio(*pmd)))
return;
__split_huge_pmd_locked(vma, pmd, address, freeze);
}