ghsa-j5v8-prgm-3f4c
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
mm/shmem, swap: fix softlockup with mTHP swapin
Following softlockup can be easily reproduced on my test machine with:
echo always > /sys/kernel/mm/transparent_hugepage/hugepages-64kB/enabled swapon /dev/zram0 # zram0 is a 48G swap device mkdir -p /sys/fs/cgroup/memory/test echo 1G > /sys/fs/cgroup/test/memory.max echo $BASHPID > /sys/fs/cgroup/test/cgroup.procs while true; do dd if=/dev/zero of=/tmp/test.img bs=1M count=5120 cat /tmp/test.img > /dev/null rm /tmp/test.img done
Then after a while: watchdog: BUG: soft lockup - CPU#0 stuck for 763s! [cat:5787] Modules linked in: zram virtiofs CPU: 0 UID: 0 PID: 5787 Comm: cat Kdump: loaded Tainted: G L 6.15.0.orig-gf3021d9246bc-dirty #118 PREEMPT(voluntary)· Tainted: [L]=SOFTLOCKUP Hardware name: Red Hat KVM/RHEL-AV, BIOS 0.0.0 02/06/2015 RIP: 0010:mpol_shared_policy_lookup+0xd/0x70 Code: e9 b8 b4 ff ff 31 c0 c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 0f 1f 44 00 00 41 54 55 53 <48> 8b 1f 48 85 db 74 41 4c 8d 67 08 48 89 fb 48 89 f5 4c 89 e7 e8 RSP: 0018:ffffc90002b1fc28 EFLAGS: 00000202 RAX: 00000000001c20ca RBX: 0000000000724e1e RCX: 0000000000000001 RDX: ffff888118e214c8 RSI: 0000000000057d42 RDI: ffff888118e21518 RBP: 000000000002bec8 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000bf4 R11: 0000000000000000 R12: 0000000000000001 R13: 00000000001c20ca R14: 00000000001c20ca R15: 0000000000000000 FS: 00007f03f995c740(0000) GS:ffff88a07ad9a000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f03f98f1000 CR3: 0000000144626004 CR4: 0000000000770eb0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: shmem_alloc_folio+0x31/0xc0 shmem_swapin_folio+0x309/0xcf0 ? filemap_get_entry+0x117/0x1e0 ? xas_load+0xd/0xb0 ? filemap_get_entry+0x101/0x1e0 shmem_get_folio_gfp+0x2ed/0x5b0 shmem_file_read_iter+0x7f/0x2e0 vfs_read+0x252/0x330 ksys_read+0x68/0xf0 do_syscall_64+0x4c/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f03f9a46991 Code: 00 48 8b 15 81 14 10 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 20 ad 01 00 f3 0f 1e fa 80 3d 35 97 10 00 00 74 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 4f c3 66 0f 1f 44 00 00 55 48 89 e5 48 83 ec RSP: 002b:00007fff3c52bd28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000040000 RCX: 00007f03f9a46991 RDX: 0000000000040000 RSI: 00007f03f98ba000 RDI: 0000000000000003 RBP: 00007fff3c52bd50 R08: 0000000000000000 R09: 00007f03f9b9a380 R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000040000 R13: 00007f03f98ba000 R14: 0000000000000003 R15: 0000000000000000
The reason is simple, readahead brought some order 0 folio in swap cache, and the swapin mTHP folio being allocated is in conflict with it, so swapcache_prepare fails and causes shmem_swap_alloc_folio to return -EEXIST, and shmem simply retries again and again causing this loop.
Fix it by applying a similar fix for anon mTHP swapin.
The performance change is very slight, time of swapin 10g zero folios with shmem (test for 12 times): Before: 2.47s After: 2.48s
[kasong@tencent.com: add comment]
{
"affected": [],
"aliases": [
"CVE-2025-38241"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-09T11:15:26Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/shmem, swap: fix softlockup with mTHP swapin\n\nFollowing softlockup can be easily reproduced on my test machine with:\n\necho always \u003e /sys/kernel/mm/transparent_hugepage/hugepages-64kB/enabled\nswapon /dev/zram0 # zram0 is a 48G swap device\nmkdir -p /sys/fs/cgroup/memory/test\necho 1G \u003e /sys/fs/cgroup/test/memory.max\necho $BASHPID \u003e /sys/fs/cgroup/test/cgroup.procs\nwhile true; do\n dd if=/dev/zero of=/tmp/test.img bs=1M count=5120\n cat /tmp/test.img \u003e /dev/null\n rm /tmp/test.img\ndone\n\nThen after a while:\nwatchdog: BUG: soft lockup - CPU#0 stuck for 763s! [cat:5787]\nModules linked in: zram virtiofs\nCPU: 0 UID: 0 PID: 5787 Comm: cat Kdump: loaded Tainted: G L 6.15.0.orig-gf3021d9246bc-dirty #118 PREEMPT(voluntary)\u00b7\nTainted: [L]=SOFTLOCKUP\nHardware name: Red Hat KVM/RHEL-AV, BIOS 0.0.0 02/06/2015\nRIP: 0010:mpol_shared_policy_lookup+0xd/0x70\nCode: e9 b8 b4 ff ff 31 c0 c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 0f 1f 44 00 00 41 54 55 53 \u003c48\u003e 8b 1f 48 85 db 74 41 4c 8d 67 08 48 89 fb 48 89 f5 4c 89 e7 e8\nRSP: 0018:ffffc90002b1fc28 EFLAGS: 00000202\nRAX: 00000000001c20ca RBX: 0000000000724e1e RCX: 0000000000000001\nRDX: ffff888118e214c8 RSI: 0000000000057d42 RDI: ffff888118e21518\nRBP: 000000000002bec8 R08: 0000000000000001 R09: 0000000000000000\nR10: 0000000000000bf4 R11: 0000000000000000 R12: 0000000000000001\nR13: 00000000001c20ca R14: 00000000001c20ca R15: 0000000000000000\nFS: 00007f03f995c740(0000) GS:ffff88a07ad9a000(0000) knlGS:0000000000000000\nCS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00007f03f98f1000 CR3: 0000000144626004 CR4: 0000000000770eb0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nPKRU: 55555554\nCall Trace:\n \u003cTASK\u003e\n shmem_alloc_folio+0x31/0xc0\n shmem_swapin_folio+0x309/0xcf0\n ? filemap_get_entry+0x117/0x1e0\n ? xas_load+0xd/0xb0\n ? filemap_get_entry+0x101/0x1e0\n shmem_get_folio_gfp+0x2ed/0x5b0\n shmem_file_read_iter+0x7f/0x2e0\n vfs_read+0x252/0x330\n ksys_read+0x68/0xf0\n do_syscall_64+0x4c/0x1c0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\nRIP: 0033:0x7f03f9a46991\nCode: 00 48 8b 15 81 14 10 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 20 ad 01 00 f3 0f 1e fa 80 3d 35 97 10 00 00 74 13 31 c0 0f 05 \u003c48\u003e 3d 00 f0 ff ff 77 4f c3 66 0f 1f 44 00 00 55 48 89 e5 48 83 ec\nRSP: 002b:00007fff3c52bd28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000\nRAX: ffffffffffffffda RBX: 0000000000040000 RCX: 00007f03f9a46991\nRDX: 0000000000040000 RSI: 00007f03f98ba000 RDI: 0000000000000003\nRBP: 00007fff3c52bd50 R08: 0000000000000000 R09: 00007f03f9b9a380\nR10: 0000000000000022 R11: 0000000000000246 R12: 0000000000040000\nR13: 00007f03f98ba000 R14: 0000000000000003 R15: 0000000000000000\n \u003c/TASK\u003e\n\nThe reason is simple, readahead brought some order 0 folio in swap cache,\nand the swapin mTHP folio being allocated is in conflict with it, so\nswapcache_prepare fails and causes shmem_swap_alloc_folio to return\n-EEXIST, and shmem simply retries again and again causing this loop.\n\nFix it by applying a similar fix for anon mTHP swapin.\n\nThe performance change is very slight, time of swapin 10g zero folios\nwith shmem (test for 12 times):\nBefore: 2.47s\nAfter: 2.48s\n\n[kasong@tencent.com: add comment]",
"id": "GHSA-j5v8-prgm-3f4c",
"modified": "2025-07-09T12:31:34Z",
"published": "2025-07-09T12:31:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38241"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1283dfc1e0cd52cf525c2cb1b59a6f9183aab7ca"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a05dd8ae5cbb1cb45f349922cfea4f548a5e5d6f"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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