Patch "nbd: fix incomplete validation of ioctl arg" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    nbd: fix incomplete validation of ioctl arg

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nbd-fix-incomplete-validation-of-ioctl-arg.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 10e7183f33b0e2868f0acd9b6e4266d0de07af6c
Author: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
Date:   Mon Feb 6 22:58:05 2023 +0800

    nbd: fix incomplete validation of ioctl arg
    
    [ Upstream commit 55793ea54d77719a071b1ccc05a05056e3b5e009 ]
    
    We tested and found an alarm caused by nbd_ioctl arg without verification.
    The UBSAN warning calltrace like below:
    
    UBSAN: Undefined behaviour in fs/buffer.c:1709:35
    signed integer overflow:
    -9223372036854775808 - 1 cannot be represented in type 'long long int'
    CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1
    Hardware name: linux,dummy-virt (DT)
    Call trace:
     dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78
     show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158
     __dump_stack lib/dump_stack.c:77 [inline]
     dump_stack+0x170/0x1dc lib/dump_stack.c:118
     ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161
     handle_overflow+0x188/0x1dc lib/ubsan.c:192
     __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206
     __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709
     block_write_full_page+0x1f0/0x280 fs/buffer.c:2934
     blkdev_writepage+0x34/0x40 fs/block_dev.c:607
     __writepage+0x68/0xe8 mm/page-writeback.c:2305
     write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240
     generic_writepages+0xdc/0x148 mm/page-writeback.c:2329
     blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114
     do_writepages+0xd4/0x250 mm/page-writeback.c:2344
    
    The reason for triggering this warning is __block_write_full_page()
    -> i_size_read(inode) - 1 overflow.
    inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> bytesize.
    We think it is necessary to limit the size of arg to prevent errors.
    
    Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int.
    Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine),
    it will become 1 after the coercion, which will return unexpected results.
    
    Fix it by adding checks to prevent passing in too large numbers.
    
    Signed-off-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
    Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
    Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230206145805.2645671-1-zhongjinghua@xxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index e379ccc63c520..888a6abb50f53 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -325,6 +325,9 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize,
 	if (blk_validate_block_size(blksize))
 		return -EINVAL;
 
+	if (bytesize < 0)
+		return -EINVAL;
+
 	nbd->config->bytesize = bytesize;
 	nbd->config->blksize_bits = __ffs(blksize);
 
@@ -1110,6 +1113,9 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 	struct nbd_sock *nsock;
 	int err;
 
+	/* Arg will be cast to int, check it to avoid overflow */
+	if (arg > INT_MAX)
+		return -EINVAL;
 	sock = nbd_get_socket(nbd, arg, &err);
 	if (!sock)
 		return err;



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