From: Shifeng Li lishifeng@sangfor.com.cn

[ Upstream commit 8f5100da56b3980276234e812ce98d8f075194cd ]

Fix a cmd->ent use after free due to a race on command entry. Such race occurs when one of the commands releases its last refcount and frees its index and entry while another process running command flush flow takes refcount to this command entry. The process which handles commands flush may see this command as needed to be flushed if the other process allocated a ent->idx but didn't set ent to cmd->ent_arr in cmd_work_handler(). Fix it by moving the assignment of cmd->ent_arr into the spin lock.

[70013.081955] BUG: KASAN: use-after-free in mlx5_cmd_trigger_completions+0x1e2/0x4c0 [mlx5_core] [70013.081967] Write of size 4 at addr ffff88880b1510b4 by task kworker/26:1/1433361 [70013.081968] [70013.082028] Workqueue: events aer_isr [70013.082053] Call Trace: [70013.082067] dump_stack+0x8b/0xbb [70013.082086] print_address_description+0x6a/0x270 [70013.082102] kasan_report+0x179/0x2c0 [70013.082173] mlx5_cmd_trigger_completions+0x1e2/0x4c0 [mlx5_core] [70013.082267] mlx5_cmd_flush+0x80/0x180 [mlx5_core] [70013.082304] mlx5_enter_error_state+0x106/0x1d0 [mlx5_core] [70013.082338] mlx5_try_fast_unload+0x2ea/0x4d0 [mlx5_core] [70013.082377] remove_one+0x200/0x2b0 [mlx5_core] [70013.082409] pci_device_remove+0xf3/0x280 [70013.082439] device_release_driver_internal+0x1c3/0x470 [70013.082453] pci_stop_bus_device+0x109/0x160 [70013.082468] pci_stop_and_remove_bus_device+0xe/0x20 [70013.082485] pcie_do_fatal_recovery+0x167/0x550 [70013.082493] aer_isr+0x7d2/0x960 [70013.082543] process_one_work+0x65f/0x12d0 [70013.082556] worker_thread+0x87/0xb50 [70013.082571] kthread+0x2e9/0x3a0 [70013.082592] ret_from_fork+0x1f/0x40

The logical relationship of this error is as follows:

aer_recover_work | ent->work -------------------------------------------+------------------------------ aer_recover_work_func | |- pcie_do_recovery | |- report_error_detected | |- mlx5_pci_err_detected |cmd_work_handler |- mlx5_enter_error_state | |- cmd_alloc_index |- enter_error_state | |- lock cmd->alloc_lock |- mlx5_cmd_flush | |- clear_bit |- mlx5_cmd_trigger_completions| |- unlock cmd->alloc_lock |- lock cmd->alloc_lock | |- vector = ~dev->cmd.vars.bitmask |- for_each_set_bit | |- cmd_ent_get(cmd->ent_arr[i]) (UAF) |- unlock cmd->alloc_lock | |- cmd->ent_arr[ent->idx]=ent

The cmd->ent_arr[ent->idx] assignment and the bit clearing are not protected by the cmd->alloc_lock in cmd_work_handler().

Fixes: 50b2412b7e78 ("net/mlx5: Avoid possible free of command entry while timeout comp handler") Reviewed-by: Moshe Shemesh moshe@nvidia.com Signed-off-by: Shifeng Li lishifeng@sangfor.com.cn Signed-off-by: Saeed Mahameed saeedm@nvidia.com [Samasth: backport for 5.4.y] Signed-off-by: Samasth Norway Ananda samasth.norway.ananda@oracle.com

Conflicts: drivers/net/ethernet/mellanox/mlx5/core/cmd.c conflict caused due to the absence of commit 58db72869a9f ("net/mlx5: Re-organize mlx5_cmd struct") which is structural change of code and is not necessary for this patch. --- commit: 50b2412b7e78 ("net/mlx5: Avoid possible free of command entry while timeout comp handler") is present from linux-5.4.y onwards but the current commit which fixes it is only present from linux-6.1.y. Would be nice to get an opinion from the author or maintainer. --- drivers/net/ethernet/mellanox/mlx5/core/cmd.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c index 93a6597366f5..ebf5b30b2100 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c @@ -114,15 +114,18 @@ static u8 alloc_token(struct mlx5_cmd *cmd) return token; }

-static int cmd_alloc_index(struct mlx5_cmd *cmd) +static int cmd_alloc_index(struct mlx5_cmd *cmd, struct mlx5_cmd_work_ent *ent) { unsigned long flags; int ret;

spin_lock_irqsave(&cmd->alloc_lock, flags); ret = find_first_bit(&cmd->bitmask, cmd->max_reg_cmds); - if (ret < cmd->max_reg_cmds) + if (ret < cmd->max_reg_cmds) { clear_bit(ret, &cmd->bitmask); + ent->idx = ret; + cmd->ent_arr[ent->idx] = ent; + } spin_unlock_irqrestore(&cmd->alloc_lock, flags);

return ret < cmd->max_reg_cmds ? ret : -ENOMEM; @@ -905,7 +908,7 @@ static void cmd_work_handler(struct work_struct *work) sem = ent->page_queue ? &cmd->pages_sem : &cmd->sem; down(sem); if (!ent->page_queue) { - alloc_ret = cmd_alloc_index(cmd); + alloc_ret = cmd_alloc_index(cmd, ent); if (alloc_ret < 0) { mlx5_core_err(dev, "failed to allocate command entry\n"); if (ent->callback) { @@ -920,15 +923,14 @@ static void cmd_work_handler(struct work_struct *work) up(sem); return; } - ent->idx = alloc_ret; } else { ent->idx = cmd->max_reg_cmds; spin_lock_irqsave(&cmd->alloc_lock, flags); clear_bit(ent->idx, &cmd->bitmask); + cmd->ent_arr[ent->idx] = ent; spin_unlock_irqrestore(&cmd->alloc_lock, flags); }

- cmd->ent_arr[ent->idx] = ent; lay = get_inst(cmd, ent->idx); ent->lay = lay; memset(lay, 0, sizeof(*lay));