| Message ID | 20241029224304.2169092-2-andrew.kanner@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | ocfs2: remove entry once instead of null-ptr-dereference in ocfs2_xa_remove() | expand |
On 10/30/24 6:43 AM, Andrew Kanner wrote: > Syzkaller is able to provoke null-ptr-dereference in ocfs2_xa_remove(): > > [ 57.319872] (a.out,1161,7):ocfs2_xa_remove:2028 ERROR: status = -12 > [ 57.320420] (a.out,1161,7):ocfs2_xa_cleanup_value_truncate:1999 ERROR: Partial truncate while removing xattr overlay.upper. Leaking 1 clusters and removing the entry > [ 57.321727] BUG: kernel NULL pointer dereference, address: 0000000000000004 > [...] > [ 57.325727] RIP: 0010:ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 > [...] > [ 57.331328] Call Trace: > [ 57.331477] <TASK> > [...] > [ 57.333511] ? do_user_addr_fault+0x3e5/0x740 > [ 57.333778] ? exc_page_fault+0x70/0x170 > [ 57.334016] ? asm_exc_page_fault+0x2b/0x30 > [ 57.334263] ? __pfx_ocfs2_xa_block_wipe_namevalue+0x10/0x10 > [ 57.334596] ? ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 > [ 57.334913] ocfs2_xa_remove_entry+0x23/0xc0 > [ 57.335164] ocfs2_xa_set+0x704/0xcf0 > [ 57.335381] ? _raw_spin_unlock+0x1a/0x40 > [ 57.335620] ? ocfs2_inode_cache_unlock+0x16/0x20 > [ 57.335915] ? trace_preempt_on+0x1e/0x70 > [ 57.336153] ? start_this_handle+0x16c/0x500 > [ 57.336410] ? preempt_count_sub+0x50/0x80 > [ 57.336656] ? _raw_read_unlock+0x20/0x40 > [ 57.336906] ? start_this_handle+0x16c/0x500 > [ 57.337162] ocfs2_xattr_block_set+0xa6/0x1e0 > [ 57.337424] __ocfs2_xattr_set_handle+0x1fd/0x5d0 > [ 57.337706] ? ocfs2_start_trans+0x13d/0x290 > [ 57.337971] ocfs2_xattr_set+0xb13/0xfb0 > [ 57.338207] ? dput+0x46/0x1c0 > [ 57.338393] ocfs2_xattr_trusted_set+0x28/0x30 > [ 57.338665] ? ocfs2_xattr_trusted_set+0x28/0x30 > [ 57.338948] __vfs_removexattr+0x92/0xc0 > [ 57.339182] __vfs_removexattr_locked+0xd5/0x190 > [ 57.339456] ? preempt_count_sub+0x50/0x80 > [ 57.339705] vfs_removexattr+0x5f/0x100 > [...] > > Reproducer uses faultinject facility to fail ocfs2_xa_remove() -> > ocfs2_xa_value_truncate() with -ENOMEM. > > In this case the comment mentions that we can return 0 if > ocfs2_xa_cleanup_value_truncate() is going to wipe the entry > anyway. But the following 'rc' check is wrong and execution flow do > 'ocfs2_xa_remove_entry(loc);' twice: > * 1st: in ocfs2_xa_cleanup_value_truncate(); > * 2nd: returning back to ocfs2_xa_remove() instead of going to 'out'. > > Fix this by skipping the 2nd removal of the same entry and making > syzkaller repro happy. > > Cc: stable@vger.kernel.org > Fixes: 399ff3a748cf ("ocfs2: Handle errors while setting external xattr values.") > Reported-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/671e13ab.050a0220.2b8c0f.01d0.GAE@google.com/T/ > Tested-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com > Signed-off-by: Andrew Kanner <andrew.kanner@gmail.com> > --- > fs/ocfs2/xattr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c > index dd0a05365e79..5bc4d660e15a 100644 > --- a/fs/ocfs2/xattr.c > +++ b/fs/ocfs2/xattr.c > @@ -2036,7 +2036,7 @@ static int ocfs2_xa_remove(struct ocfs2_xa_loc *loc, > rc = 0; > ocfs2_xa_cleanup_value_truncate(loc, "removing", > orig_clusters); > - if (rc) > + if (rc == 0) Seems in this case, we have to ignore rc and directly goto out? Thanks, Joseph > goto out; > } > }
On Fri, Nov 01, 2024 at 08:53:18PM +0800, Joseph Qi wrote: > [...] > > --- a/fs/ocfs2/xattr.c > > +++ b/fs/ocfs2/xattr.c > > @@ -2036,7 +2036,7 @@ static int ocfs2_xa_remove(struct ocfs2_xa_loc *loc, > > rc = 0; > > ocfs2_xa_cleanup_value_truncate(loc, "removing", > > orig_clusters); > > - if (rc) > > + if (rc == 0) > > Seems in this case, we have to ignore rc and directly goto out? > > Thanks, > Joseph It looks so. After ocfs2_xa_value_truncate(loc, 0, ctxt) we might have ocfs2_xa_value_clusters(loc) <= orig_clusters. But we already do everything we should for '<' case in the following ocfs2_xa_cleanup_value_truncate(). And probably should just return error code for '=' case. I'll send v2 with your suggestion. Thanks.
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c index dd0a05365e79..5bc4d660e15a 100644 --- a/fs/ocfs2/xattr.c +++ b/fs/ocfs2/xattr.c @@ -2036,7 +2036,7 @@ static int ocfs2_xa_remove(struct ocfs2_xa_loc *loc, rc = 0; ocfs2_xa_cleanup_value_truncate(loc, "removing", orig_clusters); - if (rc) + if (rc == 0) goto out; } }
Syzkaller is able to provoke null-ptr-dereference in ocfs2_xa_remove(): [ 57.319872] (a.out,1161,7):ocfs2_xa_remove:2028 ERROR: status = -12 [ 57.320420] (a.out,1161,7):ocfs2_xa_cleanup_value_truncate:1999 ERROR: Partial truncate while removing xattr overlay.upper. Leaking 1 clusters and removing the entry [ 57.321727] BUG: kernel NULL pointer dereference, address: 0000000000000004 [...] [ 57.325727] RIP: 0010:ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 [...] [ 57.331328] Call Trace: [ 57.331477] <TASK> [...] [ 57.333511] ? do_user_addr_fault+0x3e5/0x740 [ 57.333778] ? exc_page_fault+0x70/0x170 [ 57.334016] ? asm_exc_page_fault+0x2b/0x30 [ 57.334263] ? __pfx_ocfs2_xa_block_wipe_namevalue+0x10/0x10 [ 57.334596] ? ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 [ 57.334913] ocfs2_xa_remove_entry+0x23/0xc0 [ 57.335164] ocfs2_xa_set+0x704/0xcf0 [ 57.335381] ? _raw_spin_unlock+0x1a/0x40 [ 57.335620] ? ocfs2_inode_cache_unlock+0x16/0x20 [ 57.335915] ? trace_preempt_on+0x1e/0x70 [ 57.336153] ? start_this_handle+0x16c/0x500 [ 57.336410] ? preempt_count_sub+0x50/0x80 [ 57.336656] ? _raw_read_unlock+0x20/0x40 [ 57.336906] ? start_this_handle+0x16c/0x500 [ 57.337162] ocfs2_xattr_block_set+0xa6/0x1e0 [ 57.337424] __ocfs2_xattr_set_handle+0x1fd/0x5d0 [ 57.337706] ? ocfs2_start_trans+0x13d/0x290 [ 57.337971] ocfs2_xattr_set+0xb13/0xfb0 [ 57.338207] ? dput+0x46/0x1c0 [ 57.338393] ocfs2_xattr_trusted_set+0x28/0x30 [ 57.338665] ? ocfs2_xattr_trusted_set+0x28/0x30 [ 57.338948] __vfs_removexattr+0x92/0xc0 [ 57.339182] __vfs_removexattr_locked+0xd5/0x190 [ 57.339456] ? preempt_count_sub+0x50/0x80 [ 57.339705] vfs_removexattr+0x5f/0x100 [...] Reproducer uses faultinject facility to fail ocfs2_xa_remove() -> ocfs2_xa_value_truncate() with -ENOMEM. In this case the comment mentions that we can return 0 if ocfs2_xa_cleanup_value_truncate() is going to wipe the entry anyway. But the following 'rc' check is wrong and execution flow do 'ocfs2_xa_remove_entry(loc);' twice: * 1st: in ocfs2_xa_cleanup_value_truncate(); * 2nd: returning back to ocfs2_xa_remove() instead of going to 'out'. Fix this by skipping the 2nd removal of the same entry and making syzkaller repro happy. Cc: stable@vger.kernel.org Fixes: 399ff3a748cf ("ocfs2: Handle errors while setting external xattr values.") Reported-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/671e13ab.050a0220.2b8c0f.01d0.GAE@google.com/T/ Tested-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com Signed-off-by: Andrew Kanner <andrew.kanner@gmail.com> --- fs/ocfs2/xattr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)