[PATCH] fs/fuse: fix null-ptr-deref when checking SB_I_NOIDMAP flag
From: Alexander Mikhalitsyn
Date: Thu Sep 12 2024 - 10:59:02 EST
It was reported [1] that on linux-next/fs-next the following crash
is reproducible:
[ 42.659136] Oops: general protection fault, probably for non-canonical address 0xdffffc000000000b: 0000 [#1] PREEMPT SMP KASAN NOPTI
[ 42.660501] fbcon: Taking over console
[ 42.660930] KASAN: null-ptr-deref in range [0x0000000000000058-0x000000000000005f]
[ 42.661752] CPU: 1 UID: 0 PID: 1589 Comm: dtprobed Not tainted 6.11.0-rc6+ #1
[ 42.662565] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.6.6 08/22/2023
[ 42.663472] RIP: 0010:fuse_get_req+0x36b/0x990 [fuse]
[ 42.664046] Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 8c 05 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6d 08 48 8d 7d 58 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 05 00 00 f6 45 59 20 0f 85 06 03 00 00 48 83
[ 42.666945] RSP: 0018:ffffc900009a7730 EFLAGS: 00010212
[ 42.668837] RAX: dffffc0000000000 RBX: 1ffff92000134eed RCX: ffffffffc20dec9a
[ 42.670122] RDX: 000000000000000b RSI: 0000000000000008 RDI: 0000000000000058
[ 42.672154] RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed1022110172
[ 42.672160] R10: ffff888110880b97 R11: ffffc900009a737a R12: 0000000000000001
[ 42.672179] R13: ffff888110880b60 R14: ffff888110880b90 R15: ffff888169973840
[ 42.672186] FS: 00007f28cd21d7c0(0000) GS:ffff8883ef280000(0000) knlGS:0000000000000000
[ 42.672191] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 42.[ CR02: ;32m00007f3237366208 CR3: 0 OK 79e001 CR4: 0000000000770ef0
[ 42.672214] PKRU: 55555554
[ 42.672218] Call Trace:
[ 42.672223] <TASK>
[ 42.672226] ? die_addr+0x41/0xa0
[ 42.672238] ? exc_general_protection+0x14c/0x230
[ 42.672250] ? asm_exc_general_protection+0x26/0x30
[ 42.672260] ? fuse_get_req+0x77a/0x990 [fuse]
[ 42.672281] ? fuse_get_req+0x36b/0x990 [fuse]
[ 42.672300] ? kasan_unpoison+0x27/0x60
[ 42.672310] ? __pfx_fuse_get_req+0x10/0x10 [fuse]
[ 42.672327] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672333] ? alloc_pages_mpol_noprof+0x195/0x440
[ 42.672340] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672345] ? kasan_unpoison+0x27/0x60
[ 42.672350] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672355] ? __kasan_slab_alloc+0x4d/0x90
[ 42.672362] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672367] ? __kmalloc_cache_noprof+0x134/0x350
[ 42.672376] fuse_simple_background+0xe7/0x180 [fuse]
[ 42.672406] cuse_channel_open+0x540/0x710 [cuse]
[ 42.672415] misc_open+0x2a7/0x3a0
[ 42.672424] chrdev_open+0x1ef/0x5f0
[ 42.672432] ? __pfx_chrdev_open+0x10/0x10
[ 42.672439] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672443] ? security_file_open+0x3bb/0x720
[ 42.672451] do_dentry_open+0x43d/0x1200
[ 42.672459] ? __pfx_chrdev_open+0x10/0x10
[ 42.672468] vfs_open+0x79/0x340
[ 42.672475] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672482] do_open+0x68c/0x11e0
[ 42.672489] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672495] ? __pfx_do_open+0x10/0x10
[ 42.672501] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.672506] ? open_last_lookups+0x2a2/0x1370
[ 42.672515] path_openat+0x24f/0x640
[ 42.672522] ? __pfx_path_openat+0x10/0x10
[ 42.723972] ? stack_depot_save_flags+0x45/0x4b0
[ 42.724787] ? __fput+0x43c/0xa70
[ 42.725100] do_filp_open+0x1b3/0x3e0
[ 42.725710] ? poison_slab_object+0x10d/0x190
[ 42.726145] ? __kasan_slab_free+0x33/0x50
[ 42.726570] ? __pfx_do_filp_open+0x10/0x10
[ 42.726981] ? do_syscall_64+0x64/0x170
[ 42.727418] ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 42.728018] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.728505] ? do_raw_spin_lock+0x131/0x270
[ 42.728922] ? __pfx_do_raw_spin_lock+0x10/0x10
[ 42.729494] ? do_raw_spin_unlock+0x14c/0x1f0
[ 42.729992] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.730889] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.732178] ? alloc_fd+0x176/0x5e0
[ 42.732585] do_sys_openat2+0x122/0x160
[ 42.732929] ? __pfx_do_sys_openat2+0x10/0x10
[ 42.733448] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.734013] ? __pfx_map_id_up+0x10/0x10
[ 42.734482] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.735529] ? __memcg_slab_free_hook+0x292/0x500
[ 42.736131] __x64_sys_openat+0x123/0x1e0
[ 42.736526] ? __pfx___x64_sys_openat+0x10/0x10
[ 42.737369] ? __x64_sys_close+0x7c/0xd0
[ 42.737717] ? srso_alias_return_thunk+0x5/0xfbef5
[ 42.738192] ? syscall_trace_enter+0x11e/0x1b0
[ 42.738739] do_syscall_64+0x64/0x170
[ 42.739113] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 42.739638] RIP: 0033:0x7f28cd13e87b
[ 42.740038] Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 91 00 00 00 48 8b 54 24 28 64 48 2b 14 25
[ 42.741943] RSP: 002b:00007ffc992546c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
[ 42.742951] RAX: ffffffffffffffda RBX: 00007f28cd44f1ee RCX: 00007f28cd13e87b
[ 42.743660] RDX: 0000000000000002 RSI: 00007f28cd44f2fa RDI: 00000000ffffff9c
[ 42.744518] RBP: 00007f28cd44f2fa R08: 0000000000000000 R09: 0000000000000001
[ 42.745211] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
[ 42.745920] R13: 00007f28cd44f2fa R14: 0000000000000000 R15: 0000000000000003
[ 42.746708] </TASK>
[ 42.746937] Modules linked in: cuse vfat fat ext4 mbcache jbd2 intel_rapl_msr intel_rapl_common kvm_amd ccp bochs drm_vram_helper kvm drm_ttm_helper ttm pcspkr i2c_piix4 drm_kms_helper i2c_smbus pvpanic_mmio pvpanic joydev sch_fq_codel drm fuse xfs nvme_tcp nvme_fabrics nvme_core sd_mod sg virtio_net net_failover virtio_scsi failover crct10dif_pclmul crc32_pclmul ata_generic pata_acpi ata_piix ghash_clmulni_intel virtio_pci sha512_ssse3 virtio_pci_legacy_dev sha256_ssse3 virtio_pci_modern_dev sha1_ssse3 libata serio_raw dm_multipath btrfs blake2b_generic xor zstd_compress raid6_pq sunrpc dm_mirror dm_region_hash dm_log dm_mod be2iscsi bnx2i cnic uio cxgb4i cxgb4 tls cxgb3i cxgb3 mdio libcxgbi libcxgb qla4xxx iscsi_boot_sysfs iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi qemu_fw_cfg aesni_intel crypto_simd cryptd
[ 42.754333] ---[ end trace 0000000000000000 ]---
[ 42.756899] RIP: 0010:fuse_get_req+0x36b/0x990 [fuse]
[ 42.757851] Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 8c 05 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6d 08 48 8d 7d 58 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 05 00 00 f6 45 59 20 0f 85 06 03 00 00 48 83
[ 42.760334] RSP: 0018:ffffc900009a7730 EFLAGS: 00010212
[ 42.760940] RAX: dffffc0000000000 RBX: 1ffff92000134eed RCX: ffffffffc20dec9a
[ 42.761697] RDX: 000000000000000b RSI: 0000000000000008 RDI: 0000000000000058
[ 42.763009] RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed1022110172
[ 42.763920] R10: ffff888110880b97 R11: ffffc900009a737a R12: 0000000000000001
[ 42.764839] R13: ffff888110880b60 R14: ffff888110880b90 R15: ffff888169973840
[ 42.765716] FS: 00007f28cd21d7c0(0000) GS:ffff8883ef280000(0000) knlGS:0000000000000000
[ 42.766890] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 42.767828] CR2: 00007f3237366208 CR3: 000000012c79e001 CR4: 0000000000770ef0
[ 42.768730] PKRU: 55555554
[ 42.769022] Kernel panic - not syncing: Fatal exception
[ 42.770758] Kernel Offset: 0x7200000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[ 42.771947] ---[ end Kernel panic - not syncing: Fatal exception ]---
It's obviously CUSE related callstack. For CUSE case, we don't have superblock and
our checks for SB_I_NOIDMAP flag does not make any sense. Let's handle this case gracefully.
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Chandan Babu R <chandanbabu@xxxxxxxxxx>
Cc: <linux-fsdevel@xxxxxxxxxxxxxxx>
Cc: <linux-kernel@xxxxxxxxxxxxxxx>
Fixes: aa16880d9f13 ("fuse: add basic infrastructure to support idmappings")
Link: https://lore.kernel.org/linux-next/87v7z586py.fsf@debian-BULLSEYE-live-builder-AMD64/ [1]
Reported-by: Chandan Babu R <chandanbabu@xxxxxxxxxx>
Reported-by: syzbot+20c7e20cc8f5296dca12@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
---
fs/fuse/dev.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index e42b2f38d35f..84226bffc419 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -114,7 +114,7 @@ static struct fuse_req *fuse_get_req(struct mnt_idmap *idmap,
{
struct fuse_conn *fc = fm->fc;
struct fuse_req *req;
- bool no_idmap = (fm->sb->s_iflags & SB_I_NOIDMAP);
+ bool no_idmap = (!fm->sb || fm->sb->s_iflags & SB_I_NOIDMAP);
kuid_t fsuid;
kgid_t fsgid;
int err;
@@ -516,7 +516,7 @@ static void fuse_force_creds(struct fuse_req *req)
{
struct fuse_conn *fc = req->fm->fc;
- if (req->fm->sb->s_iflags & SB_I_NOIDMAP) {
+ if (!req->fm->sb || req->fm->sb->s_iflags & SB_I_NOIDMAP) {
req->in.h.uid = from_kuid_munged(fc->user_ns, current_fsuid());
req->in.h.gid = from_kgid_munged(fc->user_ns, current_fsgid());
} else {
--
2.34.1