linux-kernel - [PATCH] fscrypt: Fix null pointer when defer i_crypt

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Date:   Tue, 13 Dec 2022 16:11:03 +0800
From:   Jun Nie <jun.nie@...aro.org>
To:     tytso@....edu, jaegeuk@...nel.org, ebiggers@...nel.org,
        linux-fscrypt@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fscrypt: Fix null pointer when defer i_crypt_info

syzbot report below bug[1]. Fix it with checking null pointer before
deferring i_crypt_info.

[1]
general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 3 PID: 456 Comm: repro Not tainted 6.1.0+gc0daf896 #169
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:fscrypt_limit_io_blocks+0xfa/0x2c0
Call Trace:
 <TASK>
 ext4_iomap_begin+0x6c5/0x7e0
 ? asym_cpu_capacity_scan+0x6b0/0x6b0
 ? ext4_iomap_begin_report+0x6b0/0x6b0
 ? __sanitizer_cov_trace_const_cmp1+0x1a/0x20
 ? ext4_commit_super+0x3c1/0x560
 ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
 ? ext4_handle_error+0x3bf/0x6b0
 ? ext4_iomap_begin_report+0x6b0/0x6b0
 iomap_iter+0x538/0xc80
 iomap_bmap+0x1ed/0x2d0
 ? iomap_to_fiemap+0x220/0x220
 ? rwsem_down_read_slowpath+0xc00/0xc00
 ? __ext4_iget+0x19c/0x4370
 ext4_bmap+0x288/0x470
 ? mpage_prepare_extent_to_map+0xd80/0xd80
 bmap+0xb1/0x120
 jbd2_journal_init_inode+0x7d/0x3f0
 ? up_write+0x6c/0xb0
 ? jbd2_journal_init_dev+0x130/0x130
 ? register_shrinker+0x33/0x160
 ext4_fill_super+0xa467/0xc650
 ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
 ? ext4_reconfigure+0x2ad0/0x2ad0
 ? snprintf+0xbb/0xf0
 ? vsprintf+0x40/0x40
 ? up_write+0x6c/0xb0
 ? __sanitizer_cov_trace_cmp4+0x16/0x20
 ? set_blocksize+0x2f0/0x380
 get_tree_bdev+0x438/0x740
 ? get_tree_bdev+0x438/0x740
 ? ext4_reconfigure+0x2ad0/0x2ad0
 ext4_get_tree+0x1d/0x30
 vfs_get_tree+0x88/0x2e0
 path_mount+0x6ca/0x1ec0
 ? putname+0x110/0x150
 ? finish_automount+0x790/0x790
 ? putname+0x115/0x150
 __x64_sys_mount+0x2aa/0x340
 ? copy_mnt_ns+0xab0/0xab0
 ? __sanitizer_cov_trace_cmp4+0x16/0x20
 ? exit_to_user_mode_prepare+0x40/0x120
 do_syscall_64+0x35/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 5fee36095cda ("fscrypt: add inline encryption support")
Reported-by: syzbot+ba9dac45bc76c490b7c3@...kaller.appspotmail.com
Signed-off-by: Jun Nie <jun.nie@...aro.org>
---
 fs/crypto/inline_crypt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c
index cea8b14007e6..fec859e83774 100644
--- a/fs/crypto/inline_crypt.c
+++ b/fs/crypto/inline_crypt.c
@@ -232,7 +232,7 @@ void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
 
 bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode)
 {
-	return inode->i_crypt_info->ci_inlinecrypt;
+	return inode->i_crypt_info && inode->i_crypt_info->ci_inlinecrypt;
 }
 EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto);
 
-- 
2.34.1