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ch04: kernel panic when openning
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proc_create returns non-null pointer but open generates null-pointer
panic.
I checked the panic address. That is a code calling open.

/ # insmod share/rust_proc.ko
[   22.202776] rust_proc: module verification failed: signature and/or required key missing - tainting kernel
[   22.204453] rust_proc: rust_proc is loaded
[   22.205103] rust_proc: succeeded to create a proc entry: 0xffff8880054696c0
/ # cat /proc/rust_demo/rust_proc_fs
[   26.663960] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
[   26.665132] BUG: unable to handle page fault for address: ffff888005492a00
[   26.666141] #PF: supervisor instruction fetch in kernel mode
[   26.666674] #PF: error_code(0x0011) - permissions violation
[   26.666674] PGD 3a01067 P4D 3a01067 PUD 3a02067 PMD 80000000054001e3
[   26.666674] Oops: 0011 [#1] PREEMPT SMP NOPTI
[   26.666674] CPU: 0 PID: 120 Comm: cat Tainted: G            E      6.3.0+ Rust-for-Linux#18
[   26.666674] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
[   26.666674] RIP: 0010:0xffff888005492a00
[   26.666674] Code: 00 00 60 11 e0 81 ff ff ff ff 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 08
[   26.666674] RSP: 0018:ffff8880056c7e00 EFLAGS: 00010286
[   26.666674] RAX: ffff8880056c7918 RBX: 0000000000000000 RCX: ffff8880056c7ef0
[   26.666674] RDX: 0000000000001000 RSI: 00007ffc8b3ba048 RDI: ffff888005721400
[   26.666674] RBP: ffff8880056c7e48 R08: 00007ffc8b3ba048 R09: 0000000000000000
[   26.666674] R10: 0000000000000000 R11: ffff888005492a00 R12: ffff8880054696c0
[   26.666674] R13: ffff888005721400 R14: 0000000000000001 R15: 0000000000000000
[   26.666674] FS:  000000000249a3c0(0000) GS:ffff888007a00000(0000) knlGS:0000000000000000
[   26.666674] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   26.666674] CR2: ffff888005492a00 CR3: 00000000054c6000 CR4: 00000000000006f0
[   26.666674] Call Trace:
[   26.666674]  <TASK>
[   26.666674]  ? proc_reg_read+0xe8/0x150
[   26.666674]  vfs_read+0xb4/0x260
[   26.666674]  ? do_sendfile+0x1cf/0x3f0
[   26.666674]  ksys_read+0x5f/0xb0
[   26.666674]  __x64_sys_read+0x1b/0x20
[   26.666674]  do_syscall_64+0x35/0x50
[   26.666674]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[   26.666674] RIP: 0033:0x4ad272
[   26.666674] Code: 31 c0 e9 b1 fe ff ff 50 48 8d 3d c1 80 17 00 e8 54 8e 00 00 0f 1f 40 00 f3 0f 1e fa 64 8b 04 25 18 00 00 04
[   26.666674] RSP: 002b:00007ffc8b3b9fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[   26.666674] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004ad272
[   26.666674] RDX: 0000000000001000 RSI: 00007ffc8b3ba048 RDI: 0000000000000003
[   26.666674] RBP: 00007ffc8b3ba048 R08: 0000000000000001 R09: 0000000000000000
[   26.666674] R10: 0000000001000000 R11: 0000000000000246 R12: 0000000000001000
[   26.666674] R13: 000000000249a3a0 R14: 0000000000000000 R15: 0000000000000001
[   26.666674]  </TASK>
[   26.666674] Modules linked in: rust_proc(E)
[   26.666674] CR2: ffff888005492a00
[   26.666674] ---[ end trace 0000000000000000 ]---
[   26.666674] RIP: 0010:0xffff888005492a00
[   26.666674] Code: 00 00 60 11 e0 81 ff ff ff ff 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 08
[   26.666674] RSP: 0018:ffff8880056c7e00 EFLAGS: 00010286
[   26.666674] RAX: ffff8880056c7918 RBX: 0000000000000000 RCX: ffff8880056c7ef0
[   26.666674] RDX: 0000000000001000 RSI: 00007ffc8b3ba048 RDI: ffff888005721400
[   26.666674] RBP: ffff8880056c7e48 R08: 00007ffc8b3ba048 R09: 0000000000000000
[   26.666674] R10: 0000000000000000 R11: ffff888005492a00 R12: ffff8880054696c0
[   26.666674] R13: ffff888005721400 R14: 0000000000000001 R15: 0000000000000000
[   26.666674] FS:  000000000249a3c0(0000) GS:ffff888007a00000(0000) knlGS:0000000000000000
[   26.666674] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   26.666674] CR2: ffff888005492a00 CR3: 00000000054c6000 CR4: 00000000000006f0
[   26.666674] note: cat[120] exited with irqs disabled
Killed
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Gioh Kim committed Oct 8, 2023
1 parent 053ed38 commit f719682
Showing 1 changed file with 30 additions and 20 deletions.
50 changes: 30 additions & 20 deletions samples/rust/rust_proc.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
//! make LLVM=1 M=samples/rust

// core is from Rust compiler, not from kernel
use core::marker::PhantomPinned;
use core::ptr;

use kernel::bindings;
Expand All @@ -26,8 +27,10 @@ module! {
}

struct RustProc {
ops: bindings::proc_ops,
parent: *mut bindings::proc_dir_entry,
_entry: *mut bindings::proc_dir_entry,
_pin: PhantomPinned,
}

impl RustProc {
Expand Down Expand Up @@ -55,9 +58,13 @@ impl RustProc {
pr_info!("proc_open is invoked\n");
pr_info!("proc_open is invoked\n");
pr_info!("proc_open is invoked\n");
pr_info!("proc_open is invoked\n");
pr_info!("proc_open is invoked\n");
pr_info!("proc_open is invoked\n");
pr_err!("proc_open is invoked\n");
pr_err!("proc_open is invoked\n");
pr_err!("proc_open is invoked\n");

while true {
pr_info!("proc_open is invoked\n");
}

unsafe {
let ret = bindings::single_open(_file, Some(Self::proc_show), ptr::null_mut());
Expand All @@ -79,33 +86,36 @@ impl kernel::Module for RustProc {
let dir_name = CString::try_from_fmt(fmt!("{}", SUB_DIR_NAME))?;
let parent = bindings::proc_mkdir(dir_name.as_char_ptr(), ptr::null_mut());

let proc_ops = bindings::proc_ops {
proc_flags: 0, // mandatory to prevent build error
proc_get_unmapped_area: None, // mandatory to prevent build error
proc_read_iter: None, // mandatory to prevent build error
proc_open: Some(Self::proc_open),
proc_read: None,
proc_write: None,
proc_lseek: None,
proc_release: None,
proc_poll: None,
proc_ioctl: None,
proc_mmap: None,
let ret = Self {
parent,
ops: bindings::proc_ops {
proc_flags: 0, // mandatory to prevent build error
proc_get_unmapped_area: None, // mandatory to prevent build error
proc_read_iter: None, // mandatory to prevent build error
proc_open: Some(Self::proc_open),
proc_read: None,
proc_write: None,
proc_lseek: None,
proc_release: None,
proc_poll: None,
proc_ioctl: None,
proc_mmap: None,
},
_entry: ptr::null_mut(),
_pin: PhantomPinned,
};

let entry_name = CString::try_from_fmt(fmt!("{}", PROC_FS_NAME))?;
let entry: *mut bindings::proc_dir_entry =
bindings::proc_create(entry_name.as_char_ptr(), 0o644, parent, &proc_ops);
bindings::proc_create(entry_name.as_char_ptr(), 0o644, parent, &ret.ops);
// How to check entry?
if entry.is_null() {
pr_info!("failed to create a proc entry\n");
} else {
pr_info!("succeeded to create a proc entry: {:p}\n", entry);
}

Ok(RustProc {
parent,
_entry: entry,
})
Ok(ret)
}
}
}
Expand Down

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