From: Jakub Acs <acsjakub@amazon.de> stable inclusion from stable-v6.6.114 commit 92b82e232b8d8b116ac6e57aeae7a6033db92c60 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ID3WFZ CVE: CVE-2025-40040 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit f04aad36a07cc17b7a5d5b9a2d386ce6fae63e93 upstream. syzkaller discovered the following crash: (kernel BUG) [ 44.607039] ------------[ cut here ]------------ [ 44.607422] kernel BUG at mm/userfaultfd.c:2067! [ 44.608148] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 44.608814] CPU: 1 UID: 0 PID: 2475 Comm: reproducer Not tainted 6.16.0-rc6 #1 PREEMPT(none) [ 44.609635] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 44.610695] RIP: 0010:userfaultfd_release_all+0x3a8/0x460 <snip other registers, drop unreliable trace> [ 44.617726] Call Trace: [ 44.617926] <TASK> [ 44.619284] userfaultfd_release+0xef/0x1b0 [ 44.620976] __fput+0x3f9/0xb60 [ 44.621240] fput_close_sync+0x110/0x210 [ 44.622222] __x64_sys_close+0x8f/0x120 [ 44.622530] do_syscall_64+0x5b/0x2f0 [ 44.622840] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 44.623244] RIP: 0033:0x7f365bb3f227 Kernel panics because it detects UFFD inconsistency during userfaultfd_release_all(). Specifically, a VMA which has a valid pointer to vma->vm_userfaultfd_ctx, but no UFFD flags in vma->vm_flags. The inconsistency is caused in ksm_madvise(): when user calls madvise() with MADV_UNMEARGEABLE on a VMA that is registered for UFFD in MINOR mode, it accidentally clears all flags stored in the upper 32 bits of vma->vm_flags. Assuming x86_64 kernel build, unsigned long is 64-bit and unsigned int and int are 32-bit wide. This setup causes the following mishap during the &= ~VM_MERGEABLE assignment. VM_MERGEABLE is a 32-bit constant of type unsigned int, 0x8000'0000. After ~ is applied, it becomes 0x7fff'ffff unsigned int, which is then promoted to unsigned long before the & operation. This promotion fills upper 32 bits with leading 0s, as we're doing unsigned conversion (and even for a signed conversion, this wouldn't help as the leading bit is 0). & operation thus ends up AND-ing vm_flags with 0x0000'0000'7fff'ffff instead of intended 0xffff'ffff'7fff'ffff and hence accidentally clears the upper 32-bits of its value. Fix it by changing `VM_MERGEABLE` constant to unsigned long, using the BIT() macro. Note: other VM_* flags are not affected: This only happens to the VM_MERGEABLE flag, as the other VM_* flags are all constants of type int and after ~ operation, they end up with leading 1 and are thus converted to unsigned long with leading 1s. Note 2: After commit 31defc3b01d9 ("userfaultfd: remove (VM_)BUG_ON()s"), this is no longer a kernel BUG, but a WARNING at the same place: [ 45.595973] WARNING: CPU: 1 PID: 2474 at mm/userfaultfd.c:2067 but the root-cause (flag-drop) remains the same. [akpm@linux-foundation.org: rust bindgen wasn't able to handle BIT(), from Miguel] Link: https://lore.kernel.org/oe-kbuild-all/202510030449.VfSaAjvd-lkp@intel.com/ Link: https://lkml.kernel.org/r/20251001090353.57523-2-acsjakub@amazon.de Fixes: 7677f7fd8be7 ("userfaultfd: add minor fault registration mode") Signed-off-by: Jakub Acs <acsjakub@amazon.de> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: SeongJae Park <sj@kernel.org> Tested-by: Alice Ryhl <aliceryhl@google.com> Tested-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Cc: Xu Xin <xu.xin16@zte.com.cn> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Peter Xu <peterx@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [acsjakub@amazon.de: adapt rust bindgen const to older versions] Signed-off-by: Jakub Acs <acsjakub@amazon.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: include/linux/mm.h drivers/net/ethernet/huawei/bma/edma_drv/edma_host.h [Contlict due to additional commit f0db1bf5852542c46c16d0b305193069e265f769 ("Huawei BMA: Adding Huawei BMA driver: host_edma_drv") in OLK and some context conflicts] Signed-off-by: Quanmin Yan <yanquanmin1@huawei.com> --- drivers/net/ethernet/huawei/bma/edma_drv/edma_host.h | 2 +- include/linux/mm.h | 2 +- rust/bindings/bindings_helper.h | 2 ++ rust/bindings/lib.rs | 1 + 4 files changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/huawei/bma/edma_drv/edma_host.h b/drivers/net/ethernet/huawei/bma/edma_drv/edma_host.h index 93c81bc92286..3cb79e601af3 100644 --- a/drivers/net/ethernet/huawei/bma/edma_drv/edma_host.h +++ b/drivers/net/ethernet/huawei/bma/edma_drv/edma_host.h @@ -72,7 +72,7 @@ /* Can contain "struct page" and pure PFN pages */ #define VM_MIXEDMAP 0x10000000 -#define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */ +#define VM_MERGEABLE BIT(31) /* KSM may merge identical pages */ #if defined(CONFIG_X86) /* PAT reserves whole VMA at once (x86) */ diff --git a/include/linux/mm.h b/include/linux/mm.h index 8999dcf606fa..c0040a2014c4 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -320,7 +320,7 @@ extern unsigned int kobjsize(const void *objp); #define VM_MIXEDMAP 0x10000000 /* Can contain "struct page" and pure PFN pages */ #define VM_HUGEPAGE 0x20000000 /* MADV_HUGEPAGE marked this vma */ #define VM_NOHUGEPAGE 0x40000000 /* MADV_NOHUGEPAGE marked this vma */ -#define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */ +#define VM_MERGEABLE BIT(31) /* KSM may merge identical pages */ #ifdef CONFIG_GMEM # define VM_PEER_SHARED_BIT 56 /* movable memory between host and device */ diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index c91a3c24f607..5416f21918e0 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -12,8 +12,10 @@ #include <linux/refcount.h> #include <linux/wait.h> #include <linux/sched.h> +#include <linux/mm.h> /* `bindgen` gets confused at certain things. */ const size_t BINDINGS_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN; const gfp_t BINDINGS_GFP_KERNEL = GFP_KERNEL; const gfp_t BINDINGS___GFP_ZERO = __GFP_ZERO; +const vm_flags_t BINDINGS_VM_MERGEABLE = VM_MERGEABLE; diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs index 9bcbea04dac3..7d9078b94a8f 100644 --- a/rust/bindings/lib.rs +++ b/rust/bindings/lib.rs @@ -51,3 +51,4 @@ mod bindings_helper { pub const GFP_KERNEL: gfp_t = BINDINGS_GFP_KERNEL; pub const __GFP_ZERO: gfp_t = BINDINGS___GFP_ZERO; +pub const VM_MERGEABLE: vm_flags_t = BINDINGS_VM_MERGEABLE; -- 2.43.0