ghsa-4hg9-w486-7gv5
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
binder: fix alloc->vma_vm_mm null-ptr dereference
Syzbot reported a couple issues introduced by commit 44e602b4e52f ("binder_alloc: add missing mmap_lock calls when using the VMA"), in which we attempt to acquire the mmap_lock when alloc->vma_vm_mm has not been initialized yet.
This can happen if a binder_proc receives a transaction without having previously called mmap() to setup the binder_proc->alloc space in [1]. Also, a similar issue occurs via binder_alloc_print_pages() when we try to dump the debugfs binder stats file in [2].
Sample of syzbot's crash report: ================================================================== KASAN: null-ptr-deref in range [0x0000000000000128-0x000000000000012f] CPU: 0 PID: 3755 Comm: syz-executor229 Not tainted 6.0.0-rc1-next-20220819-syzkaller #0 syz-executor229[3755] cmdline: ./syz-executor2294415195 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 RIP: 0010:__lock_acquire+0xd83/0x56d0 kernel/locking/lockdep.c:4923 [...] Call Trace: lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 down_read+0x98/0x450 kernel/locking/rwsem.c:1499 mmap_read_lock include/linux/mmap_lock.h:117 [inline] binder_alloc_new_buf_locked drivers/android/binder_alloc.c:405 [inline] binder_alloc_new_buf+0xa5/0x19e0 drivers/android/binder_alloc.c:593 binder_transaction+0x242e/0x9a80 drivers/android/binder.c:3199 binder_thread_write+0x664/0x3220 drivers/android/binder.c:3986 binder_ioctl_write_read drivers/android/binder.c:5036 [inline] binder_ioctl+0x3470/0x6d00 drivers/android/binder.c:5323 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] ==================================================================
Fix these issues by setting up alloc->vma_vm_mm pointer during open() and caching directly from current->mm. This guarantees we have a valid reference to take the mmap_lock during scenarios described above.
[1] https://syzkaller.appspot.com/bug?extid=f7dc54e5be28950ac459 [2] https://syzkaller.appspot.com/bug?extid=a75ebe0452711c9e56d9
{
"affected": [],
"aliases": [
"CVE-2022-49947"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-06-18T11:15:21Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinder: fix alloc-\u003evma_vm_mm null-ptr dereference\n\nSyzbot reported a couple issues introduced by commit 44e602b4e52f\n(\"binder_alloc: add missing mmap_lock calls when using the VMA\"), in\nwhich we attempt to acquire the mmap_lock when alloc-\u003evma_vm_mm has not\nbeen initialized yet.\n\nThis can happen if a binder_proc receives a transaction without having\npreviously called mmap() to setup the binder_proc-\u003ealloc space in [1].\nAlso, a similar issue occurs via binder_alloc_print_pages() when we try\nto dump the debugfs binder stats file in [2].\n\nSample of syzbot\u0027s crash report:\n ==================================================================\n KASAN: null-ptr-deref in range [0x0000000000000128-0x000000000000012f]\n CPU: 0 PID: 3755 Comm: syz-executor229 Not tainted 6.0.0-rc1-next-20220819-syzkaller #0\n syz-executor229[3755] cmdline: ./syz-executor2294415195\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022\n RIP: 0010:__lock_acquire+0xd83/0x56d0 kernel/locking/lockdep.c:4923\n [...]\n Call Trace:\n \u003cTASK\u003e\n lock_acquire kernel/locking/lockdep.c:5666 [inline]\n lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631\n down_read+0x98/0x450 kernel/locking/rwsem.c:1499\n mmap_read_lock include/linux/mmap_lock.h:117 [inline]\n binder_alloc_new_buf_locked drivers/android/binder_alloc.c:405 [inline]\n binder_alloc_new_buf+0xa5/0x19e0 drivers/android/binder_alloc.c:593\n binder_transaction+0x242e/0x9a80 drivers/android/binder.c:3199\n binder_thread_write+0x664/0x3220 drivers/android/binder.c:3986\n binder_ioctl_write_read drivers/android/binder.c:5036 [inline]\n binder_ioctl+0x3470/0x6d00 drivers/android/binder.c:5323\n vfs_ioctl fs/ioctl.c:51 [inline]\n __do_sys_ioctl fs/ioctl.c:870 [inline]\n __se_sys_ioctl fs/ioctl.c:856 [inline]\n __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856\n do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80\n entry_SYSCALL_64_after_hwframe+0x63/0xcd\n [...]\n ==================================================================\n\nFix these issues by setting up alloc-\u003evma_vm_mm pointer during open()\nand caching directly from current-\u003emm. This guarantees we have a valid\nreference to take the mmap_lock during scenarios described above.\n\n[1] https://syzkaller.appspot.com/bug?extid=f7dc54e5be28950ac459\n[2] https://syzkaller.appspot.com/bug?extid=a75ebe0452711c9e56d9",
"id": "GHSA-4hg9-w486-7gv5",
"modified": "2025-06-18T12:30:36Z",
"published": "2025-06-18T12:30:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-49947"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1da52815d5f1b654c89044db0cdc6adce43da1f1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/81203ab7a6ef843a2b904a0a494f28c457d44d27"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b2a97babb0a510f8921891f9e70c5a5ef33cadac"
}
],
"schema_version": "1.4.0",
"severity": []
}
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