{
  "threat_severity" : "Moderate",
  "public_date" : "2024-04-02T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: bcachefs: grab s_umount only if snapshotting",
    "id" : "2272777",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2272777"
  },
  "cvss3" : {
    "cvss3_base_score" : "5.5",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-833",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nbcachefs: grab s_umount only if snapshotting\nWhen I was testing mongodb over bcachefs with compression,\nthere is a lockdep warning when snapshotting mongodb data volume.\n$ cat test.sh\nprog=bcachefs\n$prog subvolume create /mnt/data\n$prog subvolume create /mnt/data/snapshots\nwhile true;do\n$prog subvolume snapshot /mnt/data /mnt/data/snapshots/$(date +%s)\nsleep 1s\ndone\n$ cat /etc/mongodb.conf\nsystemLog:\ndestination: file\nlogAppend: true\npath: /mnt/data/mongod.log\nstorage:\ndbPath: /mnt/data/\nlockdep reports:\n[ 3437.452330] ======================================================\n[ 3437.452750] WARNING: possible circular locking dependency detected\n[ 3437.453168] 6.7.0-rc7-custom+ #85 Tainted: G            E\n[ 3437.453562] ------------------------------------------------------\n[ 3437.453981] bcachefs/35533 is trying to acquire lock:\n[ 3437.454325] ffffa0a02b2b1418 (sb_writers#10){.+.+}-{0:0}, at: filename_create+0x62/0x190\n[ 3437.454875]\nbut task is already holding lock:\n[ 3437.455268] ffffa0a02b2b10e0 (&type->s_umount_key#48){.+.+}-{3:3}, at: bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]\n[ 3437.456009]\nwhich lock already depends on the new lock.\n[ 3437.456553]\nthe existing dependency chain (in reverse order) is:\n[ 3437.457054]\n-> #3 (&type->s_umount_key#48){.+.+}-{3:3}:\n[ 3437.457507]        down_read+0x3e/0x170\n[ 3437.457772]        bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]\n[ 3437.458206]        __x64_sys_ioctl+0x93/0xd0\n[ 3437.458498]        do_syscall_64+0x42/0xf0\n[ 3437.458779]        entry_SYSCALL_64_after_hwframe+0x6e/0x76\n[ 3437.459155]\n-> #2 (&c->snapshot_create_lock){++++}-{3:3}:\n[ 3437.459615]        down_read+0x3e/0x170\n[ 3437.459878]        bch2_truncate+0x82/0x110 [bcachefs]\n[ 3437.460276]        bchfs_truncate+0x254/0x3c0 [bcachefs]\n[ 3437.460686]        notify_change+0x1f1/0x4a0\n[ 3437.461283]        do_truncate+0x7f/0xd0\n[ 3437.461555]        path_openat+0xa57/0xce0\n[ 3437.461836]        do_filp_open+0xb4/0x160\n[ 3437.462116]        do_sys_openat2+0x91/0xc0\n[ 3437.462402]        __x64_sys_openat+0x53/0xa0\n[ 3437.462701]        do_syscall_64+0x42/0xf0\n[ 3437.462982]        entry_SYSCALL_64_after_hwframe+0x6e/0x76\n[ 3437.463359]\n-> #1 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}:\n[ 3437.463843]        down_write+0x3b/0xc0\n[ 3437.464223]        bch2_write_iter+0x5b/0xcc0 [bcachefs]\n[ 3437.464493]        vfs_write+0x21b/0x4c0\n[ 3437.464653]        ksys_write+0x69/0xf0\n[ 3437.464839]        do_syscall_64+0x42/0xf0\n[ 3437.465009]        entry_SYSCALL_64_after_hwframe+0x6e/0x76\n[ 3437.465231]\n-> #0 (sb_writers#10){.+.+}-{0:0}:\n[ 3437.465471]        __lock_acquire+0x1455/0x21b0\n[ 3437.465656]        lock_acquire+0xc6/0x2b0\n[ 3437.465822]        mnt_want_write+0x46/0x1a0\n[ 3437.465996]        filename_create+0x62/0x190\n[ 3437.466175]        user_path_create+0x2d/0x50\n[ 3437.466352]        bch2_fs_file_ioctl+0x2ec/0xc90 [bcachefs]\n[ 3437.466617]        __x64_sys_ioctl+0x93/0xd0\n[ 3437.466791]        do_syscall_64+0x42/0xf0\n[ 3437.466957]        entry_SYSCALL_64_after_hwframe+0x6e/0x76\n[ 3437.467180]\nother info that might help us debug this:\n[ 3437.469670] 2 locks held by bcachefs/35533:\nother info that might help us debug this:\n[ 3437.467507] Chain exists of:\nsb_writers#10 --> &c->snapshot_create_lock --> &type->s_umount_key#48\n[ 3437.467979]  Possible unsafe locking scenario:\n[ 3437.468223]        CPU0                    CPU1\n[ 3437.468405]        ----                    ----\n[ 3437.468585]   rlock(&type->s_umount_key#48);\n[ 3437.468758]                                lock(&c->snapshot_create_lock);\n[ 3437.469030]                                lock(&type->s_umount_key#48);\n[ 3437.469291]   rlock(sb_writers#10);\n[ 3437.469434]\n*** DEADLOCK ***\n[ 3437.469\n---truncated---", "A vulnerability was found in the bcachefs Linux kernel module which allows to a circular locking dependency, triggering a deadlock scenario during snapshot creation operations. This occurred due to the unconditional acquisition of s_umount in __bch2_ioctl_subvolume_create(), conflicting with existing locks held by other threads which leads to a deadlock situations." ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2024-26658\nhttps://nvd.nist.gov/vuln/detail/CVE-2024-26658\nhttps://lore.kernel.org/linux-cve-announce/2024040222-CVE-2024-26658-1451@gregkh/T" ],
  "name" : "CVE-2024-26658",
  "mitigation" : {
    "value" : "Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.",
    "lang" : "en:us"
  },
  "csaw" : false
}