Messages in this thread Patch in this message | | | Date | Mon, 06 Feb 2006 20:22:48 +0530 | From | Suzuki <> | Subject | [PATCH] Fix do_path_lookup() to add the check for error in link_path_walk() |
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Hi,
I encountered an oops with 2.6.16-rc1-git3 kernel ( SLES 10 B2 kernel ), while running racer tests. The problem was hit in audit_inode() with the following stack trace :
Jan 31 19:15:27 x236 klogd:Unable to handle kernel paging request at virtual address 6b6b6b8b Jan 31 19:15:27 x236 klogd: CPU: 3 Jan 31 19:15:27 x236 klogd: EIP: 0060:[<c013ffbd>] Tainted: G U VLI Jan 31 19:15:27 x236 klogd: EFLAGS: 00010282 (2.6.16-rc1-git3-4-smp) Jan 31 19:15:27 x236 klogd: EIP is at audit_inode+0x78/0xa9 Jan 31 19:15:27 x236 klogd: eax: d29da000 ebx: ccc23638 ecx: 0000001 edx: ccc23638 Jan 31 19:15:27 x236 klogd: esi: 6b6b6b6b edi: d29da000 ebp: 0000001 esp: ce4d7ecc Jan 31 19:15:27 x236 klogd: ds: 007b es: 007b ss: 0068 Jan 31 19:15:27 x236 klogd: Process ln (pid: 12674, threadinfo=ce4d6000 task=e49df550) Jan 31 19:15:27 x236 klogd: Call Trace: Jan 31 19:15:27 x236 klogd: [<c016a843>] do_path_lookup+0x225/0x22f Jan 31 19:15:27 x236 klogd: [<c016af42>] __user_walk_fd+0x29/0x3a Jan 31 19:15:27 x236 klogd: [<c0164e7e>] vfs_stat_fd+0x15/0x3c Jan 31 19:15:27 x236 klogd: [<c014ca1c>] __handle_mm_fault+0x439/0x7a0 Jan 31 19:15:27 x236 klogd: [<c0164f32>] sys_stat64+0xf/0x23 Jan 31 19:15:27 x236 klogd: [<c0106d26>] do_syscall_trace+0x123/0x169 Jan 31 19:15:27 x236 klogd: [<c0103c09>] syscall_call+0x7/0xb
I found the root cause of the problem to be the lack of error-check in do_path_lookup() for the link_path_walk().
in do_path_lookup:
fput_light(file, fput_needed); } read_unlock(¤t->fs->lock); current->total_link_count = 0; retval = link_path_walk(name, nd); <----- No check for retval ! out: if (unlikely(current->audit_context && nd && nd->dentry && nd->dentry->d_inode)) audit_inode(name, nd->dentry->d_inode, flags); out_fail: return retval; }
If link_path_walk returns error, the inode may not be reliable. This causes the oops in audit_inode.
The bug is there in 2.6.16-rc2 also. I believe the problem in Bugme #5897 also has the same root cause, though it has different call path.
The patch attached below fixes the issue. I have tested it on 2.6.16-rc1-git3 with racer tests and it works fine.
Thanks,
Suzuki K P Linux Technology Centre IBM Software Labs,
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Fixes do_path_lookup() to avoid accessing invalid dentry or inode when the link_path_walk() has failed. This should fix Bugme #5897.
Signed Off by: Suzuki K P <suzuki@in.ibm.com>
--- fs/namei.c 2006-02-06 06:10:53.000000000 -0800 +++ fs/namei.c~fix-do-path-lookup 2006-02-06 11:33:59.000000000 -0800 @@ -1122,6 +1122,8 @@ static int fastcall do_path_lookup(int d read_unlock(¤t->fs->lock); current->total_link_count = 0; retval = link_path_walk(name, nd); + if(retval) + goto out_fail; out: if (unlikely(current->audit_context && nd && nd->dentry && nd->dentry->d_inode))
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