Messages in this thread | | | Date | Sat, 24 Feb 2018 10:32:30 -0800 | From | Eric Biggers <> | Subject | Re: [PATCH] f2fs: allocate buffer for decrypting filename to avoid panic |
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Hi Yunlong,
On Sat, Feb 24, 2018 at 05:14:58PM +0800, Yunlong Song wrote: > In some platforms (such as arm), high memory is used, then the > decrypting filename will cause panic, the reason see commit > 569cf1876a32e574ba8a7fb825cd91bafd003882 ("f2fs crypto: allocate buffer > for decrypting filename"): > > We got dentry pages from high_mem, and its address space directly goes into the > decryption path via f2fs_fname_disk_to_usr. > But, sg_init_one assumes the address is not from high_mem, so we can get this > panic since it doesn't call kmap_high but kunmap_high is triggered at the end. > > kernel BUG at ../../../../../../kernel/mm/highmem.c:290! > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM > ... > (kunmap_high+0xb0/0xb8) from [<c0114534>] (__kunmap_atomic+0xa0/0xa4) > (__kunmap_atomic+0xa0/0xa4) from [<c035f028>] (blkcipher_walk_done+0x128/0x1ec) > (blkcipher_walk_done+0x128/0x1ec) from [<c0366c24>] (crypto_cbc_decrypt+0xc0/0x170) > (crypto_cbc_decrypt+0xc0/0x170) from [<c0367148>] (crypto_cts_decrypt+0xc0/0x114) > (crypto_cts_decrypt+0xc0/0x114) from [<c035ea98>] (async_decrypt+0x40/0x48) > (async_decrypt+0x40/0x48) from [<c032ca34>] (f2fs_fname_disk_to_usr+0x124/0x304) > (f2fs_fname_disk_to_usr+0x124/0x304) from [<c03056fc>] (f2fs_fill_dentries+0xac/0x188) > (f2fs_fill_dentries+0xac/0x188) from [<c03059c8>] (f2fs_readdir+0x1f0/0x300) > (f2fs_readdir+0x1f0/0x300) from [<c0218054>] (vfs_readdir+0x90/0xb4) > (vfs_readdir+0x90/0xb4) from [<c0218418>] (SyS_getdents64+0x64/0xcc) > (SyS_getdents64+0x64/0xcc) from [<c0105ba0>] (ret_fast_syscall+0x0/0x30) > > Howerver, later patches: > commit 922ec355f86365388203672119b5bca346a45085 ("f2fs crypto: avoid > unneeded memory allocation when {en/de}crypting symlink") > commit e06f86e61d7a67fe6e826010f57aa39c674f4b1b ("f2fs crypto: avoid > unneeded memory allocation in ->readdir") > > reverts the codes, which causes panic again in arm, so let's add the old > patch again. > > Signed-off-by: Yunlong Song <yunlong.song@huawei.com> > --- > fs/f2fs/dir.c | 7 +++++++ > fs/f2fs/namei.c | 10 +++++++++- > 2 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index f00b5ed..c0cf3e7b 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -825,9 +825,16 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, > int save_len = fstr->len; > int err; > > + de_name.name = kmalloc(de_name.len, GFP_NOFS); > + if (!de_name.name) > + return -ENOMEM; > + > + memcpy(de_name.name, d->filename[bit_pos], de_name.len); > + > err = fscrypt_fname_disk_to_usr(d->inode, > (u32)de->hash_code, 0, > &de_name, fstr); > + kfree(de_name.name); > if (err) > return err; > > diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c > index c4c94c7..2cb70c1 100644 > --- a/fs/f2fs/namei.c > +++ b/fs/f2fs/namei.c > @@ -1170,8 +1170,13 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry, > > /* Symlink is encrypted */ > sd = (struct fscrypt_symlink_data *)caddr; > - cstr.name = sd->encrypted_path; > cstr.len = le16_to_cpu(sd->len); > + cstr.name = kmalloc(cstr.len, GFP_NOFS); > + if (!cstr.name) { > + res = -ENOMEM; > + goto errout; > + } > + memcpy(cstr.name, sd->encrypted_path, cstr.len); > > /* this is broken symlink case */ > if (unlikely(cstr.len == 0)) { > @@ -1198,6 +1203,8 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry, > goto errout; > } > > + kfree(cstr.name); > + > paddr = pstr.name; > > /* Null-terminate the name */ > @@ -1207,6 +1214,7 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry, > set_delayed_call(done, kfree_link, paddr); > return paddr; > errout: > + kfree(cstr.name); > fscrypt_fname_free_buffer(&pstr); > put_page(cpage); > return ERR_PTR(res); > -- > 1.8.5.2 >
The pagecache for symlinks in f2fs already uses lowmem only, so the change to ->get_link() isn't needed. Also that part of the patch doesn't apply to upstream.
For directories we may need your fix. Note: kmalloc + memcpy should be replaced with kmemdup. But alternatively, directory pages could be restricted to lowmem which would match ext4.
Eric
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