Patch "tcp: Fix shift-out-of-bounds in dctcp_update_alpha()." 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

    tcp: Fix shift-out-of-bounds in dctcp_update_alpha().

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:
     tcp-fix-shift-out-of-bounds-in-dctcp_update_alpha.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 4ca8c5a8a380bef07c4b259e69e1b7a381ebc5cd
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Fri May 17 18:16:26 2024 +0900

    tcp: Fix shift-out-of-bounds in dctcp_update_alpha().
    
    [ Upstream commit 3ebc46ca8675de6378e3f8f40768e180bb8afa66 ]
    
    In dctcp_update_alpha(), we use a module parameter dctcp_shift_g
    as follows:
    
      alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g);
      ...
      delivered_ce <<= (10 - dctcp_shift_g);
    
    It seems syzkaller started fuzzing module parameters and triggered
    shift-out-of-bounds [0] by setting 100 to dctcp_shift_g:
    
      memcpy((void*)0x20000080,
             "/sys/module/tcp_dctcp/parameters/dctcp_shift_g\000", 47);
      res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x20000080ul,
                    /*flags=*/2ul, /*mode=*/0ul);
      memcpy((void*)0x20000000, "100\000", 4);
      syscall(__NR_write, /*fd=*/r[0], /*val=*/0x20000000ul, /*len=*/4ul);
    
    Let's limit the max value of dctcp_shift_g by param_set_uint_minmax().
    
    With this patch:
    
      # echo 10 > /sys/module/tcp_dctcp/parameters/dctcp_shift_g
      # cat /sys/module/tcp_dctcp/parameters/dctcp_shift_g
      10
      # echo 11 > /sys/module/tcp_dctcp/parameters/dctcp_shift_g
      -bash: echo: write error: Invalid argument
    
    [0]:
    UBSAN: shift-out-of-bounds in net/ipv4/tcp_dctcp.c:143:12
    shift exponent 100 is too large for 32-bit type 'u32' (aka 'unsigned int')
    CPU: 0 PID: 8083 Comm: syz-executor345 Not tainted 6.9.0-05151-g1b294a1f3561 #2
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
    1.13.0-1ubuntu1.1 04/01/2014
    Call Trace:
     <TASK>
     __dump_stack lib/dump_stack.c:88 [inline]
     dump_stack_lvl+0x201/0x300 lib/dump_stack.c:114
     ubsan_epilogue lib/ubsan.c:231 [inline]
     __ubsan_handle_shift_out_of_bounds+0x346/0x3a0 lib/ubsan.c:468
     dctcp_update_alpha+0x540/0x570 net/ipv4/tcp_dctcp.c:143
     tcp_in_ack_event net/ipv4/tcp_input.c:3802 [inline]
     tcp_ack+0x17b1/0x3bc0 net/ipv4/tcp_input.c:3948
     tcp_rcv_state_process+0x57a/0x2290 net/ipv4/tcp_input.c:6711
     tcp_v4_do_rcv+0x764/0xc40 net/ipv4/tcp_ipv4.c:1937
     sk_backlog_rcv include/net/sock.h:1106 [inline]
     __release_sock+0x20f/0x350 net/core/sock.c:2983
     release_sock+0x61/0x1f0 net/core/sock.c:3549
     mptcp_subflow_shutdown+0x3d0/0x620 net/mptcp/protocol.c:2907
     mptcp_check_send_data_fin+0x225/0x410 net/mptcp/protocol.c:2976
     __mptcp_close+0x238/0xad0 net/mptcp/protocol.c:3072
     mptcp_close+0x2a/0x1a0 net/mptcp/protocol.c:3127
     inet_release+0x190/0x1f0 net/ipv4/af_inet.c:437
     __sock_release net/socket.c:659 [inline]
     sock_close+0xc0/0x240 net/socket.c:1421
     __fput+0x41b/0x890 fs/file_table.c:422
     task_work_run+0x23b/0x300 kernel/task_work.c:180
     exit_task_work include/linux/task_work.h:38 [inline]
     do_exit+0x9c8/0x2540 kernel/exit.c:878
     do_group_exit+0x201/0x2b0 kernel/exit.c:1027
     __do_sys_exit_group kernel/exit.c:1038 [inline]
     __se_sys_exit_group kernel/exit.c:1036 [inline]
     __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
     do_syscall_x64 arch/x86/entry/common.c:52 [inline]
     do_syscall_64+0xe4/0x240 arch/x86/entry/common.c:83
     entry_SYSCALL_64_after_hwframe+0x67/0x6f
    RIP: 0033:0x7f6c2b5005b6
    Code: Unable to access opcode bytes at 0x7f6c2b50058c.
    RSP: 002b:00007ffe883eb948 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
    RAX: ffffffffffffffda RBX: 00007f6c2b5862f0 RCX: 00007f6c2b5005b6
    RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
    RBP: 0000000000000001 R08: 00000000000000e7 R09: ffffffffffffffc0
    R10: 0000000000000006 R11: 0000000000000246 R12: 00007f6c2b5862f0
    R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
     </TASK>
    
    Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx>
    Reported-by: Yue Sun <samsun1006219@xxxxxxxxx>
    Reported-by: xingwei lee <xrivendell7@xxxxxxxxx>
    Closes: https://lore.kernel.org/netdev/CAEkJfYNJM=cw-8x7_Vmj1J6uYVCWMbbvD=EFmDPVBGpTsqOxEA@xxxxxxxxxxxxxx/
    Fixes: e3118e8359bb ("net: tcp: add DCTCP congestion control algorithm")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240517091626.32772-1-kuniyu@xxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index 2a6c0dd665a4c..863aab1860556 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -57,7 +57,18 @@ struct dctcp {
 };
 
 static unsigned int dctcp_shift_g __read_mostly = 4; /* g = 1/2^4 */
-module_param(dctcp_shift_g, uint, 0644);
+
+static int dctcp_shift_g_set(const char *val, const struct kernel_param *kp)
+{
+	return param_set_uint_minmax(val, kp, 0, 10);
+}
+
+static const struct kernel_param_ops dctcp_shift_g_ops = {
+	.set = dctcp_shift_g_set,
+	.get = param_get_uint,
+};
+
+module_param_cb(dctcp_shift_g, &dctcp_shift_g_ops, &dctcp_shift_g, 0644);
 MODULE_PARM_DESC(dctcp_shift_g, "parameter g for updating dctcp_alpha");
 
 static unsigned int dctcp_alpha_on_init __read_mostly = DCTCP_MAX_ALPHA;




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