linux-kernel - [PATCH v2] fs: Fix hang with BSD accounting on frozen filesystem

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sat,  4 May 2013 00:11:23 +0200
From:	Jan Kara <jack@...e.cz>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org,
	Nikola Ciprich <nikola.ciprich@...uxbox.cz>,
	LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>
Subject: [PATCH v2] fs: Fix hang with BSD accounting on frozen filesystem

When BSD process accounting is enabled and logs information to a
filesystem which gets frozen, system easily becomes unusable because
each attempt to account process information blocks. Thus e.g. every task
gets blocked in exit.

It seems better to drop accounting information (which can already happen
when filesystem is running out of space) instead of locking system up.
So we just skip the write if the filesystem is frozen.

Reported-by: Nikola Ciprich <nikola.ciprich@...uxbox.cz>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 kernel/acct.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

  Hi Al!

  I'm sending an updated fix for BSD process accounting hang. Can you please
merge it? Thanks!
								Honza

diff --git a/kernel/acct.c b/kernel/acct.c
index 85389fe..04606cc 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -540,10 +540,15 @@ static void do_acct_process(struct bsd_acct_struct *acct,
 	ac.ac_swaps = encode_comp_t(0);
 
 	/*
+	 * Get freeze protection. If the fs is frozen, just skip the write
+	 * as we could deadlock the system otherwise.
+	 */
+	if (!sb_start_write_trylock(file_inode(file)->i_sb))
+		goto out;
+	/*
 	 * Kernel segment override to datasegment and write it
 	 * to the accounting file.
 	 */
-	file_start_write(file);
 	fs = get_fs();
 	set_fs(KERNEL_DS);
 	/*
@@ -555,7 +560,7 @@ static void do_acct_process(struct bsd_acct_struct *acct,
 			       sizeof(acct_t), &file->f_pos);
 	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
 	set_fs(fs);
-	file_end_write(file);
+	sb_end_write(file_inode(file)->i_sb);
 out:
 	revert_creds(orig_cred);
 }
-- 
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/