fix(usercmd): Fix buffer overflow in uc_list() (#23225)

fix(usercmd): fix buffer overflow in uc_list()

Build with: -Wp,-D_FORTIFY_SOURCE=3 -O1 and gcc 13.

*** buffer overflow detected ***: terminated

(gdb) bt
  #0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
  #1  0x00007f3eb8b93c03 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
  #2  0x00007f3eb8b42aee in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
  #3  0x00007f3eb8b2b87f in __GI_abort () at abort.c:79
  #4  0x00007f3eb8b2c60f in __libc_message (fmt=fmt@entry=0x7f3eb8ca72e6 "*** %s ***: terminated\n") at ../sysdeps/posix/libc_fatal.c:150
  #5  0x00007f3eb8c27b29 in __GI___fortify_fail (msg=msg@entry=0x7f3eb8ca728c "buffer overflow detected") at fortify_fail.c:24
  #6  0x00007f3eb8c26364 in __GI___chk_fail () at chk_fail.c:28
  #7  0x00007f3eb8c25f45 in ___snprintf_chk (s=s@entry=0x55b8c7c096a5 <IObuff+5> "t' item", maxlen=maxlen@entry=1025, flag=flag@entry=2, slen=slen@entry=1020, format=format@entry=0x55b8c7b872a6 "%ldc") at snprintf_chk.c:29
  #8  0x000055b8c7aea59f in snprintf (__fmt=0x55b8c7b872a6 "%ldc", __n=1025, __s=0x55b8c7c096a5 <IObuff+5> "t' item") at /usr/include/bits/stdio2.h:54
  #9  uc_list (name=name@entry=0x55b8c8351788 "Explore", name_len=name_len@entry=7) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/usercmd.c:534
  #10 0x000055b8c7aeb8a0 in ex_command (eap=0x7fffdc350e60) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/usercmd.c:1009
  #11 0x000055b8c7972537 in execute_cmd0 (retv=retv@entry=0x7fffdc350e54, eap=eap@entry=0x7fffdc350e60, errormsg=errormsg@entry=0x7fffdc350e58, preview=preview@entry=false) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/ex_docmd.c:1620
  #12 0x000055b8c7975c55 in do_one_cmd (cmdlinep=cmdlinep@entry=0x7fffdc3510b8, flags=flags@entry=0, cstack=cstack@entry=0x7fffdc351140, fgetline=fgetline@entry=0x55b8c79882b8 <getexline>, cookie=cookie@entry=0x0) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/ex_docmd.c:2279
  #13 0x000055b8c79767fe in do_cmdline (cmdline=<optimized out>, fgetline=0x55b8c79882b8 <getexline>, cookie=0x0, flags=0) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/ex_docmd.c:578
  #14 0x000055b8c7a17463 in nv_colon (cap=0x7fffdc351780) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/normal.c:3228
  #15 0x000055b8c7a11b35 in normal_execute (state=0x7fffdc351700, key=<optimized out>) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/normal.c:1196
  #16 0x000055b8c7ab0994 in state_enter (s=0x7fffdc351700) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/state.c:99
  #17 0x000055b8c7a0ef68 in normal_enter (cmdwin=false, noexmode=false) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/normal.c:497
  #18 0x000055b8c78a0640 in main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/neovim-0.9.0-1.fc38.x86_64/src/nvim/main.c:641

2 files changed, 24 insertions, 15 deletions

diff --git a/src/nvim/usercmd.c b/src/nvim/usercmd.c
index e859a96552..0aacc73529 100644
--- a/src/nvim/usercmd.c
+++ b/src/nvim/usercmd.c
@@ -469,7 +469,7 @@ static void uc_list(char *name, size_t name_len)
       }
 
       // Special cases
-      int len = 4;
+      size_t len = 4;
       if (a & EX_BANG) {
         msg_putchar('!');
         len--;
@@ -491,7 +491,7 @@ static void uc_list(char *name, size_t name_len)
       }
 
       msg_outtrans_attr(cmd->uc_name, HL_ATTR(HLF_D));
-      len = (int)strlen(cmd->uc_name) + 4;
+      len = strlen(cmd->uc_name) + 4;
 
       do {
         msg_putchar(' ');
@@ -500,7 +500,7 @@ static void uc_list(char *name, size_t name_len)
 
       // "over" is how much longer the name is than the column width for
       // the name, we'll try to align what comes after.
-      const int over = len - 22;
+      const int64_t over = (int64_t)len - 22;
       len = 0;
 
       // Arguments
@@ -524,20 +524,22 @@ static void uc_list(char *name, size_t name_len)
 
       do {
         IObuff[len++] = ' ';
-      } while (len < 5 - over);
+      } while ((int64_t)len < 5 - over);
 
       // Address / Range
       if (a & (EX_RANGE | EX_COUNT)) {
         if (a & EX_COUNT) {
           // -count=N
-          snprintf(IObuff + len, IOSIZE, "%" PRId64 "c", cmd->uc_def);
-          len += (int)strlen(IObuff + len);
+          int rc = snprintf(IObuff + len, IOSIZE - len, "%" PRId64 "c", cmd->uc_def);
+          assert(rc > 0);
+          len += (size_t)rc;
         } else if (a & EX_DFLALL) {
           IObuff[len++] = '%';
         } else if (cmd->uc_def >= 0) {
           // -range=N
-          snprintf(IObuff + len, IOSIZE, "%" PRId64 "", cmd->uc_def);
-          len += (int)strlen(IObuff + len);
+          int rc = snprintf(IObuff + len, IOSIZE - len, "%" PRId64 "", cmd->uc_def);
+          assert(rc > 0);
+          len += (size_t)rc;
         } else {
           IObuff[len++] = '.';
         }
@@ -545,32 +547,34 @@ static void uc_list(char *name, size_t name_len)
 
       do {
         IObuff[len++] = ' ';
-      } while (len < 8 - over);
+      } while ((int64_t)len < 8 - over);
 
       // Address Type
       for (j = 0; addr_type_complete[j].expand != ADDR_NONE; j++) {
         if (addr_type_complete[j].expand != ADDR_LINES
             && addr_type_complete[j].expand == cmd->uc_addr_type) {
-          STRCPY(IObuff + len, addr_type_complete[j].shortname);
-          len += (int)strlen(IObuff + len);
+          int rc = snprintf(IObuff + len, IOSIZE - len, "%s", addr_type_complete[j].shortname);
+          assert(rc > 0);
+          len += (size_t)rc;
           break;
         }
       }
 
       do {
         IObuff[len++] = ' ';
-      } while (len < 13 - over);
+      } while ((int64_t)len < 13 - over);
 
       // Completion
       char *cmd_compl = get_command_complete(cmd->uc_compl);
       if (cmd_compl != NULL) {
-        STRCPY(IObuff + len, get_command_complete(cmd->uc_compl));
-        len += (int)strlen(IObuff + len);
+        int rc = snprintf(IObuff + len, IOSIZE - len, "%s", get_command_complete(cmd->uc_compl));
+        assert(rc > 0);
+        len += (size_t)rc;
       }
 
       do {
         IObuff[len++] = ' ';
-      } while (len < 25 - over);
+      } while ((int64_t)len < 25 - over);
 
       IObuff[len] = '\0';
       msg_outtrans(IObuff);
diff --git a/test/functional/ex_cmds/excmd_spec.lua b/test/functional/ex_cmds/excmd_spec.lua
index b313d6428c..14cc2b8387 100644
--- a/test/functional/ex_cmds/excmd_spec.lua
+++ b/test/functional/ex_cmds/excmd_spec.lua
@@ -28,6 +28,11 @@ describe('Ex cmds', function()
     assert_alive()
   end)
 
+  it('listing long user command does not crash', function()
+    command('execute "command" repeat("T", 255) ":"')
+    command('command')
+  end)
+
   it(':def is an unknown command #23149', function()
     eq('Vim:E492: Not an editor command: def', pcall_err(command, 'def'))
     eq(1, funcs.exists(':d'))