net: ethernet: ti: am65-cpsw: Fix segmentation fault at module unload
CVE: CVE-2022-49847
Component: kernel
Severity: Moderate
CVSS v3: 5.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Release date: 2022-01-01T00:00:00+00:00

In the Linux kernel, the following vulnerability has been resolved:

net: ethernet: ti: am65-cpsw: Fix segmentation fault at module unload

Move am65_cpsw_nuss_phylink_cleanup() call to after
am65_cpsw_nuss_cleanup_ndev() so phylink is still valid
to prevent the below Segmentation fault on module remove when
first slave link is up.

[   31.652944] Unable to handle kernel paging request at virtual address 00040008000005f4
[   31.684627] Mem abort info:
[   31.687446]   ESR = 0x0000000096000004
[   31.704614]   EC = 0x25: DABT (current EL), IL = 32 bits
[   31.720663]   SET = 0, FnV = 0
[   31.723729]   EA = 0, S1PTW = 0
[   31.740617]   FSC = 0x04: level 0 translation fault
[   31.756624] Data abort info:
[   31.759508]   ISV = 0, ISS = 0x00000004
[   31.776705]   CM = 0, WnR = 0
[   31.779695] [00040008000005f4] address between user and kernel address ranges
[   31.808644] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[   31.814928] Modules linked in: wlcore_sdio wl18xx wlcore mac80211 libarc4 cfg80211 rfkill crct10dif_ce phy_gmii_sel ti_am65_cpsw_nuss(-) sch_fq_codel ipv6
[   31.828776] CPU: 0 PID: 1026 Comm: modprobe Not tainted 6.1.0-rc2-00012-gfabfcf7dafdb-dirty #160
[   31.837547] Hardware name: Texas Instruments AM625 (DT)
[   31.842760] pstate: 40000005 (nZcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   31.849709] pc : phy_stop+0x18/0xf8
[   31.853202] lr : phylink_stop+0x38/0xf8
[   31.857031] sp : ffff80000a0839f0
[   31.860335] x29: ffff80000a0839f0 x28: ffff000000de1c80 x27: 0000000000000000
[   31.867462] x26: 0000000000000000 x25: 0000000000000000 x24: ffff80000a083b98
[   31.874589] x23: 0000000000000800 x22: 0000000000000001 x21: ffff000001bfba90
[   31.881715] x20: ffff0000015ee000 x19: 0004000800000200 x18: 0000000000000000
[   31.888842] x17: ffff800076c45000 x16: ffff800008004000 x15: 000058e39660b106
[   31.895969] x14: 0000000000000144 x13: 0000000000000144 x12: 0000000000000000
[   31.903095] x11: 000000000000275f x10: 00000000000009e0 x9 : ffff80000a0837d0
[   31.910222] x8 : ffff000000de26c0 x7 : ffff00007fbd6540 x6 : ffff00007fbd64c0
[   31.917349] x5 : ffff00007fbd0b10 x4 : ffff00007fbd0b10 x3 : ffff00007fbd3920
[   31.924476] x2 : d0a07fcff8b8d500 x1 : 0000000000000000 x0 : 0004000800000200
[   31.931603] Call trace:
[   31.934042]  phy_stop+0x18/0xf8
[   31.937177]  phylink_stop+0x38/0xf8
[   31.940657]  am65_cpsw_nuss_ndo_slave_stop+0x28/0x1e0 [ti_am65_cpsw_nuss]
[   31.947452]  __dev_close_many+0xa4/0x140
[   31.951371]  dev_close_many+0x84/0x128
[   31.955115]  unregister_netdevice_many+0x130/0x6d0
[   31.959897]  unregister_netdevice_queue+0x94/0xd8
[   31.964591]  unregister_netdev+0x24/0x38
[   31.968504]  am65_cpsw_nuss_cleanup_ndev.isra.0+0x48/0x70 [ti_am65_cpsw_nuss]
[   31.975637]  am65_cpsw_nuss_remove+0x58/0xf8 [ti_am65_cpsw_nuss]

Statement: This patch fixes a segmentation fault that occurred when unloading the ti_am65_cpsw_nuss module if the PHY link was still active. The issue stemmed from calling am65_cpsw_nuss_phylink_cleanup() too early, which invalidated the phylink structure before it was used in the network device cleanup routine. The fix moves the cleanup call to after am65_cpsw_nuss_cleanup_ndev() to maintain correct resource ordering. Without this fix, unloading the driver under certain runtime conditions (e.g., active link) would lead to a kernel oops and possible system instability due to invalid memory access.

Remediation: