CVE-2022-49753: In the Linux kernel, the following vulnerability has been resolved:  dmaengine: Fix double increment of client_count in dma_chan_get()  The first time dma_chan_get() is called for a channel the channel client_count is incorrectly incremented twice for public channels, first in balance_ref_count(), and again prior to returning. This results in an incorrect client count which will lead to the channel resources not being freed when they should be. A simple  test of repeated module load and unload of async_tx on a Dell  Power Edge R7425 also shows this resulting in a kref underflow  warning.  [  124.329662] async_tx: api initialized (async) [  129.000627] async_tx: api initialized (async) [  130.047839] ------------[ cut here ]------------ [  130.052472] refcount_t: underflow; use-after-free. [  130.057279] WARNING: CPU: 3 PID: 19364 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x110 [  130.065811] Modules linked in: async_tx(-) rfkill intel_rapl_msr intel_rapl_common amd64_edac edac_mce_amd ipmi_ssif kvm_amd dcdbas kvm mgag200 drm_shmem_helper acpi_ipmi irqbypass drm_kms_helper ipmi_si syscopyarea sysfillrect rapl pcspkr ipmi_devintf sysimgblt fb_sys_fops k10temp i2c_piix4 ipmi_msghandler acpi_power_meter acpi_cpufreq vfat fat drm fuse xfs libcrc32c sd_mod t10_pi sg ahci crct10dif_pclmul libahci crc32_pclmul crc32c_intel ghash_clmulni_intel igb megaraid_sas i40e libata i2c_algo_bit ccp sp5100_tco dca dm_mirror dm_region_hash dm_log dm_mod [last unloaded: async_tx] [  130.117361] CPU: 3 PID: 19364 Comm: modprobe Kdump: loaded Not tainted 5.14.0-185.el9.x86_64 #1 [  130.126091] Hardware name: Dell Inc. PowerEdge R7425/02MJ3T, BIOS 1.18.0 01/17/2022 [  130.133806] RIP: 0010:refcount_warn_saturate+0xba/0x110 [  130.139041] Code: 01 01 e8 6d bd 55 00 0f 0b e9 72 9d 8a 00 80 3d 26 18 9c 01 00 75 85 48 c7 c7 f8 a3 03 9d c6 05 16 18 9c 01 01 e8 4a bd 55 00 <0f> 0b e9 4f 9d 8a 00 80 3d 01 18 9c 01 00 0f 85 5e ff ff ff 48 c7 [  130.157807] RSP: 0018:ffffbf98898afe68 EFLAGS: 00010286 [  130.163036] RAX: 0000000000000000 RBX: ffff9da06028e598 RCX: 0000000000000000 [  130.170172] RDX: ffff9daf9de26480 RSI: ffff9daf9de198a0 RDI: ffff9daf9de198a0 [  130.177316] RBP: ffff9da7cddf3970 R08: 0000000000000000 R09: 00000000ffff7fff [  130.184459] R10: ffffbf98898afd00 R11: ffffffff9d9e8c28 R12: ffff9da7cddf1970 [  130.191596] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [  130.198739] FS:  00007f646435c740(0000) GS:ffff9daf9de00000(0000) knlGS:0000000000000000 [  130.206832] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [  130.212586] CR2: 00007f6463b214f0 CR3: 00000008ab98c000 CR4: 00000000003506e0 [  130.219729] Call Trace: [  130.222192]  <TASK> [  130.224305]  dma_chan_put+0x10d/0x110 [  130.227988]  dmaengine_put+0x7a/0xa0 [  130.231575]  __do_sys_delete_module.constprop.0+0x178/0x280 [  130.237157]  ? syscall_trace_enter.constprop.0+0x145/0x1d0 [  130.242652]  do_syscall_64+0x5c/0x90 [  130.246240]  ? exc_page_fault+0x62/0x150 [  130.250178]  entry_SYSCALL_64_after_hwframe+0x63/0xcd [  130.255243] RIP: 0033:0x7f6463a3f5ab [  130.258830] Code: 73 01 c3 48 8b 0d 75 a8 1b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 45 a8 1b 00 f7 d8 64 89 01 48 [  130.277591] RSP: 002b:00007fff22f972c8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0 [  130.285164] RAX: ffffffffffffffda RBX: 000055b6786edd40 RCX: 00007f6463a3f5ab [  130.292303] RDX: 0000000000000000 RSI: 0000000000000800 RDI: 000055b6786edda8 [  130.299443] RBP: 000055b6786edd40 R08: 0000000000000000 R09: 0000000000000000 [  130.306584] R10: 00007f6463b9eac0 R11: 0000000000000206 R12: 000055b6786edda8 [  130.313731] R13: 0000000000000000 R14: 000055b6786edda8 R15: 00007fff22f995f8 [  130.320875]  </TASK> [  130.323081] ---[ end trace eff7156d56b5cf25 ]---  cat /sys/class/dma/dma0chan*/in_use would get the wrong result. 2 2 2  Test-by: Jie Hai <haijie1@huawei.com>