This is a note to let you know that I've just added the patch titled s390/zcore: fix race when reading from hardware system area to the 5.4-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: s390-zcore-fix-race-when-reading-from-hardware-syste.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1b785cc75d0cb20f0f202cc6555536b275575574 Author: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Date: Tue Jul 19 07:16:33 2022 +0200 s390/zcore: fix race when reading from hardware system area [ Upstream commit 9ffed254d938c9e99eb7761c7f739294c84e0367 ] Memory buffer used for reading out data from hardware system area is not protected against concurrent access. Reported-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Fixes: 411ed3225733 ("[S390] zfcpdump support.") Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Tested-by: Alexander Egorenkov <egorenar@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/e68137f0f9a0d2558f37becc20af18e2939934f6.1658206891.git.agordeev@xxxxxxxxxxxxx Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/s390/char/zcore.c b/drivers/s390/char/zcore.c index 08f812475f5e..c9d172510509 100644 --- a/drivers/s390/char/zcore.c +++ b/drivers/s390/char/zcore.c @@ -53,6 +53,7 @@ static struct dentry *zcore_reipl_file; static struct dentry *zcore_hsa_file; static struct ipl_parameter_block *zcore_ipl_block; +static DEFINE_MUTEX(hsa_buf_mutex); static char hsa_buf[PAGE_SIZE] __aligned(PAGE_SIZE); /* @@ -69,19 +70,24 @@ int memcpy_hsa_user(void __user *dest, unsigned long src, size_t count) if (!hsa_available) return -ENODATA; + mutex_lock(&hsa_buf_mutex); while (count) { if (sclp_sdias_copy(hsa_buf, src / PAGE_SIZE + 2, 1)) { TRACE("sclp_sdias_copy() failed\n"); + mutex_unlock(&hsa_buf_mutex); return -EIO; } offset = src % PAGE_SIZE; bytes = min(PAGE_SIZE - offset, count); - if (copy_to_user(dest, hsa_buf + offset, bytes)) + if (copy_to_user(dest, hsa_buf + offset, bytes)) { + mutex_unlock(&hsa_buf_mutex); return -EFAULT; + } src += bytes; dest += bytes; count -= bytes; } + mutex_unlock(&hsa_buf_mutex); return 0; } @@ -99,9 +105,11 @@ int memcpy_hsa_kernel(void *dest, unsigned long src, size_t count) if (!hsa_available) return -ENODATA; + mutex_lock(&hsa_buf_mutex); while (count) { if (sclp_sdias_copy(hsa_buf, src / PAGE_SIZE + 2, 1)) { TRACE("sclp_sdias_copy() failed\n"); + mutex_unlock(&hsa_buf_mutex); return -EIO; } offset = src % PAGE_SIZE; @@ -111,6 +119,7 @@ int memcpy_hsa_kernel(void *dest, unsigned long src, size_t count) dest += bytes; count -= bytes; } + mutex_unlock(&hsa_buf_mutex); return 0; }