CVE-2023-53668
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix deadloop issue on reading trace_pipe Soft lockup occurs when reading file 'trace_pipe': watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [cat:4488] [...] RIP: 0010:ring_buffer_empty_cpu+0xed/0x170 RSP: 0018:ffff88810dd6fc48 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffffff93d1aaeb RDX: ffff88810a280040 RSI: 0000000000000008 RDI: ffff88811164b218 RBP: ffff88811164b218 R08: 0000000000000000 R09: ffff88815156600f R10: ffffed102a2acc01 R11: 0000000000000001 R12: 0000000051651901 R13: 0000000000000000 R14: ffff888115e49500 R15: 0000000000000000 [...] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8d853c2000 CR3: 000000010dcd8000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __find_next_entry+0x1a8/0x4b0 ? peek_next_entry+0x250/0x250 ? down_write+0xa5/0x120 ? down_write_killable+0x130/0x130 trace_find_next_entry_inc+0x3b/0x1d0 tracing_read_pipe+0x423/0xae0 ? tracing_splice_read_pipe+0xcb0/0xcb0 vfs_read+0x16b/0x490 ksys_read+0x105/0x210 ? __ia32_sys_pwrite64+0x200/0x200 ? switch_fpu_return+0x108/0x220 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x61/0xc6 Through the vmcore, I found it's because in tracing_read_pipe(), ring_buffer_empty_cpu() found some buffer is not empty but then it cannot read anything due to "rb_num_of_entries() == 0" always true, Then it infinitely loop the procedure due to user buffer not been filled, see following code path: tracing_read_pipe() { ... ... waitagain: tracing_wait_pipe() // 1. find non-empty buffer here trace_find_next_entry_inc() // 2. loop here try to find an entry __find_next_entry() ring_buffer_empty_cpu(); // 3. find non-empty buffer peek_next_entry() // 4. but peek always return NULL ring_buffer_peek() rb_buffer_peek() rb_get_reader_page() // 5. because rb_num_of_entries() == 0 always true here // then return NULL // 6. user buffer not been filled so goto 'waitgain' // and eventually leads to an deadloop in kernel!!! } By some analyzing, I found that when resetting ringbuffer, the 'entries' of its pages are not all cleared (see rb_reset_cpu()). Then when reducing the ringbuffer, and if some reduced pages exist dirty 'entries' data, they will be added into 'cpu_buffer->overrun' (see rb_remove_pages()), which cause wrong 'overrun' count and eventually cause the deadloop issue. To fix it, we need to clear every pages in rb_reset_cpu().
View original CVE JSON
{
"id": "CVE-2023-53668",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-10-07T16:15:50.640",
"lastModified": "2026-11-05T21:17:31.333",
"vulnStatus": "Analyzed",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Fix deadloop issue on reading trace_pipe\n\nSoft lockup occurs when reading file 'trace_pipe':\n\n watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [cat:4488]\n [...]\n RIP: 0010:ring_buffer_empty_cpu+0xed/0x170\n RSP: 0018:ffff88810dd6fc48 EFLAGS: 00000246\n RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffffff93d1aaeb\n RDX: ffff88810a280040 RSI: 0000000000000008 RDI: ffff88811164b218\n RBP: ffff88811164b218 R08: 0000000000000000 R09: ffff88815156600f\n R10: ffffed102a2acc01 R11: 0000000000000001 R12: 0000000051651901\n R13: 0000000000000000 R14: ffff888115e49500 R15: 0000000000000000\n [...]\n CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n CR2: 00007f8d853c2000 CR3: 000000010dcd8000 CR4: 00000000000006e0\n DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\n DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\n Call Trace:\n __find_next_entry+0x1a8/0x4b0\n ? peek_next_entry+0x250/0x250\n ? down_write+0xa5/0x120\n ? down_write_killable+0x130/0x130\n trace_find_next_entry_inc+0x3b/0x1d0\n tracing_read_pipe+0x423/0xae0\n ? tracing_splice_read_pipe+0xcb0/0xcb0\n vfs_read+0x16b/0x490\n ksys_read+0x105/0x210\n ? __ia32_sys_pwrite64+0x200/0x200\n ? switch_fpu_return+0x108/0x220\n do_syscall_64+0x33/0x40\n entry_SYSCALL_64_after_hwframe+0x61/0xc6\n\nThrough the vmcore, I found it's because in tracing_read_pipe(),\nring_buffer_empty_cpu() found some buffer is not empty but then it\ncannot read anything due to \"rb_num_of_entries() == 0\" always true,\nThen it infinitely loop the procedure due to user buffer not been\nfilled, see following code path:\n\n tracing_read_pipe() {\n ... ...\n waitagain:\n tracing_wait_pipe() // 1. find non-empty buffer here\n trace_find_next_entry_inc() // 2. loop here try to find an entry\n __find_next_entry()\n ring_buffer_empty_cpu(); // 3. find non-empty buffer\n peek_next_entry() // 4. but peek always return NULL\n ring_buffer_peek()\n rb_buffer_peek()\n rb_get_reader_page()\n // 5. because rb_num_of_entries() == 0 always true here\n // then return NULL\n // 6. user buffer not been filled so goto 'waitgain'\n // and eventually leads to an deadloop in kernel!!!\n }\n\nBy some analyzing, I found that when resetting ringbuffer, the 'entries'\nof its pages are not all cleared (see rb_reset_cpu()). Then when reducing\nthe ringbuffer, and if some reduced pages exist dirty 'entries' data, they\nwill be added into 'cpu_buffer->overrun' (see rb_remove_pages()), which\ncause wrong 'overrun' count and eventually cause the deadloop issue.\n\nTo fix it, we need to clear every pages in rb_reset_cpu()."
}
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