WARNING in ext2_new_blocks

Status: upstream: reported C repro on 2026/08/31 07:04
Reported-by: syzbot+00ce9ece44d395606bae@syzkaller.appspotmail.com
First crash: 22d, last: 22d
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[BUG] ext2: WARNING in ext2_get_group_desc when allocating a block 1 (1) 2026/09/21 07:43

Sample crash report:
EXT2-fs (loop0): (no)user_xattr optionsnot supported
EXT2-fs (loop0): warning: mounting ext3 filesystem as ext2
------------[ cut here ]------------
block_group >= groups_count - block_group = 7, groups_count = 1
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 ext2_new_blocks+0xdf4/0x117c fs/ext2/balloc.c:1280
Modules linked in:
CPU: 0 PID: 4496 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
pc : ext2_new_blocks+0xdf4/0x117c fs/ext2/balloc.c:1280
lr : ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
lr : ext2_new_blocks+0xdf4/0x117c fs/ext2/balloc.c:1280
sp : ffff8000213572c0
x29: ffff800021357380 x28: 0000000000010000 x27: ffff800021357500
x26: dfff800000000000 x25: 0000000000000007 x24: 1ffff0000426aea4
x23: ffff0000d54e1000 x22: ffff0000d37d0000 x21: 0000000000000001
x20: 000000000000ffff x19: ffff0000d54e1030 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b9ea98 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033e703a3 x12: 0000000000000000
x11: ff00800008195f68 x10: 0000000000000000 x9 : 23bbfe008e73de00
x8 : 23bbfe008e73de00 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800021356d58 x4 : ffff800015474e80 x3 : ffff800008540dd8
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
 ext2_new_blocks+0xdf4/0x117c fs/ext2/balloc.c:1280
 ext2_alloc_blocks fs/ext2/inode.c:418 [inline]
 ext2_alloc_branch fs/ext2/inode.c:487 [inline]
 ext2_get_blocks+0xc68/0x1b7c fs/ext2/inode.c:730
 ext2_get_block+0xc8/0x3ec fs/ext2/inode.c:787
 __block_write_begin_int+0x3d8/0x13c0 fs/buffer.c:1991
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin+0x98/0x11c fs/buffer.c:2102
 ext2_write_begin+0x44/0x88 fs/ext2/inode.c:903
 generic_perform_write+0x240/0x508 mm/filemap.c:3862
 __generic_file_write_iter+0x130/0x250 mm/filemap.c:3960
 generic_file_write_iter+0xb4/0x2b0 mm/filemap.c:3989
 ext2_file_write_iter+0xc0/0x3fc fs/ext2/file.c:179
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x178/0x210 fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 5972
hardirqs last  enabled at (5971): [<ffff8000083138a0>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (5972): [<ffff800011b9acd4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (5892): [<ffff800008031254>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (5890): [<ffff800008031220>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
block_group >= groups_count - block_group = 207715, groups_count = 1
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
Modules linked in:
CPU: 0 PID: 4496 Comm: syz.0.17 Tainted: G        W          syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
pc : read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
lr : ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
lr : read_block_bitmap+0x1ec/0x754 fs/ext2/balloc.c:136
sp : ffff800021357590
x29: ffff8000213575c0 x28: ffff0000d37d0678 x27: dfff800000000000
x26: 1fffe0001a6fa0cf x25: ffff0000d37d0678 x24: ffff0000d54e1000
x23: 0000000000032b63 x22: ffff0000d54e1000 x21: 0000000000000001
x20: ffff0000d37d0000 x19: 0000000000032b63 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b9ea98 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033e703a3 x12: 0000000000000000
x11: ff00800008195f68 x10: 0000000000000000 x9 : 23bbfe008e73de00
x8 : 23bbfe008e73de00 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800021357018 x4 : ffff800015474e80 x3 : ffff800008540dd8
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
 read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
 ext2_free_blocks+0x290/0x9ac fs/ext2/balloc.c:521
 ext2_free_data fs/ext2/inode.c:1099 [inline]
 __ext2_truncate_blocks+0x2b8/0xbe8 fs/ext2/inode.c:1190
 ext2_truncate_blocks fs/ext2/inode.c:1259 [inline]
 ext2_write_failed+0x1fc/0x270 fs/ext2/inode.c:65
 ext2_write_begin+0x70/0x88 fs/ext2/inode.c:905
 generic_perform_write+0x240/0x508 mm/filemap.c:3862
 __generic_file_write_iter+0x130/0x250 mm/filemap.c:3960
 generic_file_write_iter+0xb4/0x2b0 mm/filemap.c:3989
 ext2_file_write_iter+0xc0/0x3fc fs/ext2/file.c:179
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x178/0x210 fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 6100
hardirqs last  enabled at (6099): [<ffff8000083138a0>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (6100): [<ffff800011b9acd4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (6034): [<ffff8000081ae3b4>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last  enabled at (6034): [<ffff8000081ae3b4>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (5975): [<ffff800008020e6c>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
block_group >= groups_count - block_group = 3, groups_count = 1
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
Modules linked in:
CPU: 0 PID: 4496 Comm: syz.0.17 Tainted: G        W          syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
pc : read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
lr : ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
lr : read_block_bitmap+0x1ec/0x754 fs/ext2/balloc.c:136
sp : ffff800021357590
x29: ffff8000213575c0 x28: ffff0000d37d0678 x27: dfff800000000000
x26: 1fffe0001a6fa0cf x25: ffff0000d37d0678 x24: ffff0000d54e1000
x23: 0000000000000003 x22: ffff0000d54e1000 x21: 0000000000000001
x20: ffff0000d37d0000 x19: 0000000000000003 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b9ea98 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033e703a3 x12: 0000000000000000
x11: ff00800008195f68 x10: 0000000000000000 x9 : 23bbfe008e73de00
x8 : 23bbfe008e73de00 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800021357018 x4 : ffff800015474e80 x3 : ffff800008540dd8
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
 read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
 ext2_free_blocks+0x290/0x9ac fs/ext2/balloc.c:521
 ext2_free_data fs/ext2/inode.c:1099 [inline]
 __ext2_truncate_blocks+0x2b8/0xbe8 fs/ext2/inode.c:1190
 ext2_truncate_blocks fs/ext2/inode.c:1259 [inline]
 ext2_write_failed+0x1fc/0x270 fs/ext2/inode.c:65
 ext2_write_begin+0x70/0x88 fs/ext2/inode.c:905
 generic_perform_write+0x240/0x508 mm/filemap.c:3862
 __generic_file_write_iter+0x130/0x250 mm/filemap.c:3960
 generic_file_write_iter+0xb4/0x2b0 mm/filemap.c:3989
 ext2_file_write_iter+0xc0/0x3fc fs/ext2/file.c:179
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x178/0x210 fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 6182
hardirqs last  enabled at (6181): [<ffff8000083138a0>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (6182): [<ffff800011b9acd4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (6160): [<ffff8000081ae3b4>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last  enabled at (6160): [<ffff8000081ae3b4>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (6103): [<ffff800008020e6c>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
block_group >= groups_count - block_group = 7, groups_count = 1
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
WARNING: CPU: 0 PID: 4496 at fs/ext2/balloc.c:51 read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
Modules linked in:
CPU: 0 PID: 4496 Comm: syz.0.17 Tainted: G        W          syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
pc : read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
lr : ext2_get_group_desc fs/ext2/balloc.c:49 [inline]
lr : read_block_bitmap+0x1ec/0x754 fs/ext2/balloc.c:136
sp : ffff800021357590
x29: ffff8000213575c0 x28: ffff0000d37d0678 x27: dfff800000000000
x26: 1fffe0001a6fa0cf x25: ffff0000d37d0678 x24: ffff0000d54e1000
x23: 0000000000000007 x22: ffff0000d54e1000 x21: 0000000000000001
x20: ffff0000d37d0000 x19: 0000000000000007 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b9ea98 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033e703a3 x12: 0000000000000000
x11: ff00800008195f68 x10: 0000000000000000 x9 : 23bbfe008e73de00
x8 : 23bbfe008e73de00 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800021357018 x4 : ffff800015474e80 x3 : ffff800008540dd8
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 ext2_get_group_desc fs/ext2/balloc.c:-1 [inline]
 read_block_bitmap+0x1f0/0x754 fs/ext2/balloc.c:136
 ext2_free_blocks+0x290/0x9ac fs/ext2/balloc.c:521
 ext2_free_data fs/ext2/inode.c:1108 [inline]
 __ext2_truncate_blocks+0x38c/0xbe8 fs/ext2/inode.c:1190
 ext2_truncate_blocks fs/ext2/inode.c:1259 [inline]
 ext2_write_failed+0x1fc/0x270 fs/ext2/inode.c:65
 ext2_write_begin+0x70/0x88 fs/ext2/inode.c:905
 generic_perform_write+0x240/0x508 mm/filemap.c:3862
 __generic_file_write_iter+0x130/0x250 mm/filemap.c:3960
 generic_file_write_iter+0xb4/0x2b0 mm/filemap.c:3989
 ext2_file_write_iter+0xc0/0x3fc fs/ext2/file.c:179
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x178/0x210 fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 6230
hardirqs last  enabled at (6229): [<ffff8000083138a0>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (6230): [<ffff800011b9acd4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (6208): [<ffff8000081ae3b4>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last  enabled at (6208): [<ffff8000081ae3b4>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (6185): [<ffff800008020e6c>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/31 07:03 linux-6.1.y d64a499eea6b 2f52988a .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2] ci2-linux-6-1-kasan-arm64 WARNING in ext2_new_blocks
* Struck through repros no longer work on HEAD.