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memory leak in iovec_from_user (2)

syzbot syzbot 2 participants 5 messages Nov 10, 2025 io_uring

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author syzbot
#0 lore raw

Hello,

syzbot found the following issue on:

HEAD commit:    4a0c9b339199 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12af5342580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cb128cd5cb439809
dashboard link: https://syzkaller.appspot.com/bug?extid=3c93637d7648c24e1fd0
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16af5342580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13664412580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bfd02a09ef4d/disk-4a0c9b33.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ed9a1334f973/vmlinux-4a0c9b33.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e503329437ee/bzImage-4a0c9b33.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
BUG: memory leak
unreferenced object 0xffff88812638cc20 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88812638cc40 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88812638cc60 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88812638cc80 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88812638cca0 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff88812638ccc0 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF

---
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https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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#syz undup

maintainer
#1 lore raw
Quoted 44 lines · syzbot

Hello,

syzbot found the following issue on:

HEAD commit:    4a0c9b339199 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12af5342580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cb128cd5cb439809
dashboard link: https://syzkaller.appspot.com/bug?extid=3c93637d7648c24e1fd0
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16af5342580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13664412580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bfd02a09ef4d/disk-4a0c9b33.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ed9a1334f973/vmlinux-4a0c9b33.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e503329437ee/bzImage-4a0c9b33.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
BUG: memory leak
unreferenced object 0xffff88812638cc20 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
Quoted 8 lines
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

This one doesn't make any sense to me. The reproducer given only uses a single segment, and hence could never hit the allocation path for an iovec, it'd always just use the embedded vec?!

Signature · 1 line
Jens Axboe
maintainer
#2 lore raw
Quoted 54 lines · Jens Axboe
Quoted 44 lines · syzbot

Hello,

syzbot found the following issue on:

HEAD commit:    4a0c9b339199 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12af5342580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cb128cd5cb439809
dashboard link: https://syzkaller.appspot.com/bug?extid=3c93637d7648c24e1fd0
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16af5342580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13664412580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bfd02a09ef4d/disk-4a0c9b33.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ed9a1334f973/vmlinux-4a0c9b33.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e503329437ee/bzImage-4a0c9b33.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by [email protected]
BUG: memory leak
unreferenced object 0xffff88812638cc20 (size 32):
  comm "syz.0.17", pid 6104, jiffies 4294942640
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4975 [inline]
    slab_alloc_node mm/slub.c:5280 [inline]
    __do_kmalloc_node mm/slub.c:5641 [inline]
    __kmalloc_noprof+0x3e3/0x6b0 mm/slub.c:5654
    kmalloc_noprof include/linux/slab.h:961 [inline]
    kmalloc_array_noprof include/linux/slab.h:1003 [inline]
    iovec_from_user lib/iov_iter.c:1309 [inline]
    iovec_from_user+0x108/0x140 lib/iov_iter.c:1292
    __import_iovec+0x71/0x350 lib/iov_iter.c:1363
    io_import_vec io_uring/rw.c:99 [inline]
    __io_import_rw_buffer+0x1e2/0x260 io_uring/rw.c:120
    io_import_rw_buffer io_uring/rw.c:139 [inline]
    io_rw_do_import io_uring/rw.c:314 [inline]
    io_prep_rw+0xb5/0x120 io_uring/rw.c:326
    io_prep_rwv io_uring/rw.c:344 [inline]
Quoted 8 lines
    io_prep_readv+0x20/0x80 io_uring/rw.c:359
    io_init_req io_uring/io_uring.c:2248 [inline]
    io_submit_sqe io_uring/io_uring.c:2295 [inline]
    io_submit_sqes+0x354/0xe80 io_uring/io_uring.c:2447
    __do_sys_io_uring_enter+0x83f/0xcf0 io_uring/io_uring.c:3514
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f
Quoted 3 lines

This one doesn't make any sense to me. The reproducer given only uses a single segment, and hence could never hit the allocation path for an iovec, it'd always just use the embedded vec?!

Ah nevermind, I see what this is now. We can still alloc for lower counts, if we don't have a persistent one already.

Signature · 1 line
Jens Axboe
maintainer
#3 lore raw

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git io_uring-6.18

--
Jens Axboe

author syzbot Tested-by
#4 lore raw
syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by [email protected]
Tested-by [email protected]

Tested on:

commit:         4ff33a31 io_uring/rw: ensure allocated iovec gets clea..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git io_uring-6.18
console output: https://syzkaller.appspot.com/x/log.txt?x=174a317c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa4513d3a243489e
dashboard link: https://syzkaller.appspot.com/bug?extid=3c93637d7648c24e1fd0
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.