[syzbot] [fs?] BUG: unable to handle kernel NULL pointer dereference in read_cache_folio

[syzbot <syzbot+4089e577072948ac5531@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    88264981f208 Merge tag 'sched_ext-for-6.12' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16084107980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ba9c4620d9519d1f
dashboard link: https://syzkaller.appspot.com/bug?extid=4089e577072948ac5531
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11084107980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10a0d880580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/384ffdcca292/non_bootable_disk-88264981.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e96d7b6835d2/vmlinux-88264981.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0e1e66778641/Image-88264981.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4089e577072948ac5531@syzkaller.appspotmail.com

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
  ESR = 0x0000000086000006
  EC = 0x21: IABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
user pgtable: 4k pages, 52-bit VAs, pgdp=00000000462cce00
[0000000000000000] pgd=080000004468e003, p4d=08000000466cc003, pud=0800000046cd6003, pmd=0000000000000000
Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 UID: 0 PID: 3265 Comm: syz-executor218 Tainted: G    B              6.11.0-syzkaller-08481-g88264981f208 #0
Tainted: [B]=BAD_PAGE
Hardware name: linux,dummy-virt (DT)
pstate: 61400809 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=-c)
pc : 0x0
lr : filemap_read_folio+0x44/0xf4 mm/filemap.c:2363
sp : ffff800088e6bac0
x29: ffff800088e6bac0 x28: f1f000000474e000 x27: 0000000020ffd000
x26: 0000000000000000 x25: 0000000000000000 x24: 0000000002100cca
x23: f6f0000006cd5c00 x22: 0000000000000000 x21: f6f0000006cd5c00
x20: 0000000000000000 x19: ffffc1ffc02e3300 x18: ffff800088e6bc20
x17: ffff8000804fee60 x16: ffff80008052fe10 x15: 0000000000000001
x14: 0000000000000000 x13: 0000000000000003 x12: 00000000000706a3
x11: 0000000000000001 x10: ffff800081f19060 x9 : 0000000000000000
x8 : fff07ffffd1f0000 x7 : fff000007f8e9d60 x6 : 0000000000000002
x5 : ffffc1ffc02e3300 x4 : 0000000000000000 x3 : faf0000005491240
x2 : 0000000000000000 x1 : ffffc1ffc02e3300 x0 : f6f0000006cd5c00
Call trace:
 0x0
 do_read_cache_folio+0x18c/0x29c mm/filemap.c:3821
 read_cache_folio+0x14/0x20 mm/filemap.c:3853
 freader_get_folio+0x1a8/0x1f8 lib/buildid.c:72
 freader_fetch+0x44/0x164 lib/buildid.c:115
 __build_id_parse.isra.0+0x98/0x2a8 lib/buildid.c:300
 build_id_parse+0x18/0x24 lib/buildid.c:354
 do_procmap_query+0x670/0x7a0 fs/proc/task_mmu.c:534
 procfs_procmap_ioctl+0x2c/0x44 fs/proc/task_mmu.c:613
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __arm64_sys_ioctl+0xac/0xf0 fs/ioctl.c:893
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151
 el0_svc+0x34/0xec arch/arm64/kernel/entry-common.c:712
 el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:598
Code: ???????? ???????? ???????? ???????? (????????) 
---[ end trace 0000000000000000 ]---


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