| Message ID | E1tsiI6-002iMG-Kh@kylie.crudebyte.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fs/9p: fix NULL pointer dereference on mkdir | expand |
On Thursday, March 13, 2025 1:59:32 PM CET Christian Schoenebeck wrote: > When a 9p tree was mounted with option 'posixacl', parent directory had a > default ACL set for its subdirectories, e.g.: > > setfacl -m default:group:simpsons:rwx parentdir > > then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in > function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL > (since dafbe689736) even though the subsequent v9fs_set_create_acl() call > expects a valid non-NULL 'fid' pointer: > > [ 37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000 > ... > [ 37.322338] Call Trace: > [ 37.323043] <TASK> > [ 37.323621] ? __die+0x1f/0x60 > [ 37.324448] ? page_fault_oops+0x158/0x470 > [ 37.325532] ? search_module_extables+0x4a/0x80 > [ 37.326742] ? p9_client_walk+0x1c/0x2c0 [9pnet] > [ 37.328006] ? search_bpf_extables+0x5b/0x80 > [ 37.329142] ? exc_page_fault+0x72/0x190 > [ 37.330196] ? asm_exc_page_fault+0x22/0x30 > [ 37.331330] ? p9_client_walk+0x1c/0x2c0 [9pnet] > [ 37.332562] ? v9fs_fid_xattr_get+0x59/0x120 [9p] > [ 37.333824] v9fs_fid_xattr_set+0x6f/0x130 [9p] > [ 37.335077] v9fs_set_acl+0x82/0xc0 [9p] > [ 37.336112] v9fs_set_create_acl+0x41/0x60 [9p] > [ 37.337326] v9fs_vfs_mkdir_dotl+0x20d/0x2e0 [9p] > [ 37.338590] vfs_mkdir+0x192/0x250 > [ 37.339535] do_mkdirat+0x135/0x160 > [ 37.340465] __x64_sys_mkdir+0x42/0x60 > [ 37.341455] do_syscall_64+0x4b/0x110 > [ 37.342447] entry_SYSCALL_64_after_hwframe+0x76/0x7e Oops, forgot to decode the trace back: [ 37.322338] Call Trace: [ 37.323043] <TASK> [ 37.323621] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434) [ 37.324448] ? page_fault_oops (arch/x86/mm/fault.c:714) [ 37.325532] ? search_module_extables (kernel/module/main.c:3733) [ 37.326742] ? p9_client_walk (net/9p/client.c:1165) 9pnet [ 37.328006] ? search_bpf_extables (kernel/bpf/core.c:804) [ 37.329142] ? exc_page_fault (./arch/x86/include/asm/paravirt.h:686 arch/x86/mm/fault.c:1488 arch/x86/mm/fault.c:1538) [ 37.330196] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:574) [ 37.331330] ? p9_client_walk (net/9p/client.c:1165) 9pnet [ 37.332562] ? v9fs_fid_xattr_get (fs/9p/xattr.c:30) 9p [ 37.333824] v9fs_fid_xattr_set (fs/9p/fid.h:23 fs/9p/xattr.c:121) 9p [ 37.335077] v9fs_set_acl (fs/9p/acl.c:276) 9p [ 37.336112] v9fs_set_create_acl (fs/9p/acl.c:307) 9p [ 37.337326] v9fs_vfs_mkdir_dotl (fs/9p/vfs_inode_dotl.c:411) 9p [ 37.338590] vfs_mkdir (fs/namei.c:4313) [ 37.339535] do_mkdirat (fs/namei.c:4336) [ 37.340465] __x64_sys_mkdir (fs/namei.c:4354) [ 37.341455] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) [ 37.342447] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Dominique, do you want me to send a v2 or would you update the commit log on your end? /Christian > Fix this by simply swapping the sequence of these two calls in > v9fs_vfs_mkdir_dotl(), i.e. calling v9fs_set_create_acl() before > v9fs_fid_add(). > > Fixes: dafbe689736 ('9p fid refcount: cleanup p9_fid_put calls') > Reported-by: syzbot+5b667f9a1fee4ba3775a@syzkaller.appspotmail.com > Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com> > --- > fs/9p/vfs_inode_dotl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c > index 143ac03b7425..3397939fd2d5 100644 > --- a/fs/9p/vfs_inode_dotl.c > +++ b/fs/9p/vfs_inode_dotl.c > @@ -407,8 +407,8 @@ static int v9fs_vfs_mkdir_dotl(struct mnt_idmap *idmap, > err); > goto error; > } > - v9fs_fid_add(dentry, &fid); > v9fs_set_create_acl(inode, fid, dacl, pacl); > + v9fs_fid_add(dentry, &fid); > d_instantiate(dentry, inode); > err = 0; > inc_nlink(dir); >
Christian Schoenebeck wrote on Thu, Mar 13, 2025 at 02:29:42PM +0100: > On Thursday, March 13, 2025 1:59:32 PM CET Christian Schoenebeck wrote: > > When a 9p tree was mounted with option 'posixacl', parent directory had a > > default ACL set for its subdirectories, e.g.: > > > > setfacl -m default:group:simpsons:rwx parentdir > > > > then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in > > function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL > > (since dafbe689736) even though the subsequent v9fs_set_create_acl() call > > expects a valid non-NULL 'fid' pointer: > > > > [ 37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000 > > ... > > [ 37.322338] Call Trace: > > [ 37.323043] <TASK> > > [ 37.323621] ? __die+0x1f/0x60 > > [ 37.324448] ? page_fault_oops+0x158/0x470 > > [ 37.325532] ? search_module_extables+0x4a/0x80 > > [ 37.326742] ? p9_client_walk+0x1c/0x2c0 [9pnet] > > [ 37.328006] ? search_bpf_extables+0x5b/0x80 > > [ 37.329142] ? exc_page_fault+0x72/0x190 > > [ 37.330196] ? asm_exc_page_fault+0x22/0x30 > > [ 37.331330] ? p9_client_walk+0x1c/0x2c0 [9pnet] > > [ 37.332562] ? v9fs_fid_xattr_get+0x59/0x120 [9p] > > [ 37.333824] v9fs_fid_xattr_set+0x6f/0x130 [9p] > > [ 37.335077] v9fs_set_acl+0x82/0xc0 [9p] > > [ 37.336112] v9fs_set_create_acl+0x41/0x60 [9p] > > [ 37.337326] v9fs_vfs_mkdir_dotl+0x20d/0x2e0 [9p] > > [ 37.338590] vfs_mkdir+0x192/0x250 > > [ 37.339535] do_mkdirat+0x135/0x160 > > [ 37.340465] __x64_sys_mkdir+0x42/0x60 > > [ 37.341455] do_syscall_64+0x4b/0x110 > > [ 37.342447] entry_SYSCALL_64_after_hwframe+0x76/0x7e > > Oops, forgot to decode the trace back: > > [ 37.322338] Call Trace: > [ 37.323043] <TASK> > [ 37.323621] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434) > [ 37.324448] ? page_fault_oops (arch/x86/mm/fault.c:714) > [ 37.325532] ? search_module_extables (kernel/module/main.c:3733) > [ 37.326742] ? p9_client_walk (net/9p/client.c:1165) 9pnet > [ 37.328006] ? search_bpf_extables (kernel/bpf/core.c:804) > [ 37.329142] ? exc_page_fault (./arch/x86/include/asm/paravirt.h:686 arch/x86/mm/fault.c:1488 arch/x86/mm/fault.c:1538) > [ 37.330196] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:574) > [ 37.331330] ? p9_client_walk (net/9p/client.c:1165) 9pnet > [ 37.332562] ? v9fs_fid_xattr_get (fs/9p/xattr.c:30) 9p > [ 37.333824] v9fs_fid_xattr_set (fs/9p/fid.h:23 fs/9p/xattr.c:121) 9p > [ 37.335077] v9fs_set_acl (fs/9p/acl.c:276) 9p > [ 37.336112] v9fs_set_create_acl (fs/9p/acl.c:307) 9p > [ 37.337326] v9fs_vfs_mkdir_dotl (fs/9p/vfs_inode_dotl.c:411) 9p > [ 37.338590] vfs_mkdir (fs/namei.c:4313) > [ 37.339535] do_mkdirat (fs/namei.c:4336) > [ 37.340465] __x64_sys_mkdir (fs/namei.c:4354) > [ 37.341455] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) > [ 37.342447] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) > > Dominique, do you want me to send a v2 or would you update the commit log on > your end? Thank you for the quick patch! I can update the message on my end unless there's another reason to send a v2 Looks good to me, I'll test a bit over the weekend and send to Linus in the merge window in a couple of weeks (I guess it could be sent right away...)
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 143ac03b7425..3397939fd2d5 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -407,8 +407,8 @@ static int v9fs_vfs_mkdir_dotl(struct mnt_idmap *idmap, err); goto error; } - v9fs_fid_add(dentry, &fid); v9fs_set_create_acl(inode, fid, dacl, pacl); + v9fs_fid_add(dentry, &fid); d_instantiate(dentry, inode); err = 0; inc_nlink(dir);
When a 9p tree was mounted with option 'posixacl', parent directory had a default ACL set for its subdirectories, e.g.: setfacl -m default:group:simpsons:rwx parentdir then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL (since dafbe689736) even though the subsequent v9fs_set_create_acl() call expects a valid non-NULL 'fid' pointer: [ 37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 37.322338] Call Trace: [ 37.323043] <TASK> [ 37.323621] ? __die+0x1f/0x60 [ 37.324448] ? page_fault_oops+0x158/0x470 [ 37.325532] ? search_module_extables+0x4a/0x80 [ 37.326742] ? p9_client_walk+0x1c/0x2c0 [9pnet] [ 37.328006] ? search_bpf_extables+0x5b/0x80 [ 37.329142] ? exc_page_fault+0x72/0x190 [ 37.330196] ? asm_exc_page_fault+0x22/0x30 [ 37.331330] ? p9_client_walk+0x1c/0x2c0 [9pnet] [ 37.332562] ? v9fs_fid_xattr_get+0x59/0x120 [9p] [ 37.333824] v9fs_fid_xattr_set+0x6f/0x130 [9p] [ 37.335077] v9fs_set_acl+0x82/0xc0 [9p] [ 37.336112] v9fs_set_create_acl+0x41/0x60 [9p] [ 37.337326] v9fs_vfs_mkdir_dotl+0x20d/0x2e0 [9p] [ 37.338590] vfs_mkdir+0x192/0x250 [ 37.339535] do_mkdirat+0x135/0x160 [ 37.340465] __x64_sys_mkdir+0x42/0x60 [ 37.341455] do_syscall_64+0x4b/0x110 [ 37.342447] entry_SYSCALL_64_after_hwframe+0x76/0x7e Fix this by simply swapping the sequence of these two calls in v9fs_vfs_mkdir_dotl(), i.e. calling v9fs_set_create_acl() before v9fs_fid_add(). Fixes: dafbe689736 ('9p fid refcount: cleanup p9_fid_put calls') Reported-by: syzbot+5b667f9a1fee4ba3775a@syzkaller.appspotmail.com Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com> --- fs/9p/vfs_inode_dotl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)