Messages in this thread | | | Subject | Re: [PATCH] ocfs2: mount fails with buffer overflow in strlen | From | Joseph Qi <> | Date | Tue, 28 Sep 2021 20:05:22 +0800 |
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On 9/27/21 11:44 PM, Valentin Vidic wrote: > Starting with kernel v5.11 mouting an ocfs2 filesystem with either o2cb > or pcmk cluster stack fails with the trace below. Problem seems to be > that strings for cluster stack and cluster name are not guaranteed to be > null terminated in the disk representation, while strlcpy assumes that > the source string is always null terminated. This causes a read outside > of the source string triggering the buffer overflow detection. >
strlcpy in ocfs2_initialize_super() is introduced 8 years ago, so I don't understand why you've mentioned that the issues starts from v5.11.
osb->osb_cluster_stack and osb->osb_cluster_name is always larger by 1 than which in ocfs2_cluster_info, and the input size of strlcpy does the same, so I don't see how it overflows.
Thanks, Joseph
> detected buffer overflow in strlen > ------------[ cut here ]------------ > kernel BUG at lib/string.c:1149! > invalid opcode: 0000 [#1] SMP PTI > CPU: 1 PID: 910 Comm: mount.ocfs2 Not tainted 5.14.0-1-amd64 #1 > Debian 5.14.6-2 > RIP: 0010:fortify_panic+0xf/0x11 > ... > Call Trace: > ocfs2_initialize_super.isra.0.cold+0xc/0x18 [ocfs2] > ocfs2_fill_super+0x359/0x19b0 [ocfs2] > mount_bdev+0x185/0x1b0 > ? ocfs2_remount+0x440/0x440 [ocfs2] > legacy_get_tree+0x27/0x40 > vfs_get_tree+0x25/0xb0 > path_mount+0x454/0xa20 > __x64_sys_mount+0x103/0x140 > do_syscall_64+0x3b/0xc0 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Signed-off-by: Valentin Vidic <vvidic@valentin-vidic.from.hr> > --- > fs/ocfs2/super.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c > index c86bd4e60e20..1dea535224df 100644 > --- a/fs/ocfs2/super.c > +++ b/fs/ocfs2/super.c > @@ -2169,9 +2169,10 @@ static int ocfs2_initialize_super(struct super_block *sb, > if (ocfs2_clusterinfo_valid(osb)) { > osb->osb_stackflags = > OCFS2_RAW_SB(di)->s_cluster_info.ci_stackflags; > - strlcpy(osb->osb_cluster_stack, > + memcpy(osb->osb_cluster_stack, > OCFS2_RAW_SB(di)->s_cluster_info.ci_stack, > - OCFS2_STACK_LABEL_LEN + 1); > + OCFS2_STACK_LABEL_LEN); > + osb->osb_cluster_stack[OCFS2_STACK_LABEL_LEN] = '\0'; > if (strlen(osb->osb_cluster_stack) != OCFS2_STACK_LABEL_LEN) { > mlog(ML_ERROR, > "couldn't mount because of an invalid " > @@ -2180,9 +2181,10 @@ static int ocfs2_initialize_super(struct super_block *sb, > status = -EINVAL; > goto bail; > } > - strlcpy(osb->osb_cluster_name, > + memcpy(osb->osb_cluster_name, > OCFS2_RAW_SB(di)->s_cluster_info.ci_cluster, > - OCFS2_CLUSTER_NAME_LEN + 1); > + OCFS2_CLUSTER_NAME_LEN); > + osb->osb_cluster_name[OCFS2_CLUSTER_NAME_LEN] = '\0'; > } else { > /* The empty string is identical with classic tools that > * don't know about s_cluster_info. */ >
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