ash: fix incorrect path in describe_command

$ PATH=/extra/path:/usr/sbin:/usr/bin:/sbin:/bin \
> busybox sh -xc 'command -V ls; command -V ls; command -Vp ls; command -vp ls'
+ command -V ls
ls is /bin/ls
+ command -V ls
ls is a tracked alias for /bin/ls
+ command -Vp ls
ls is a tracked alias for (null)
+ command -vp ls
Segmentation fault

describe_command should respect `path' argument. Looking up in the hash table
may gives incorrect index in entry.u.index and finally causes incorrect output
or SIGSEGV.

function                                             old     new   delta
describe_command                                     386     313     -73

Signed-off-by: Youfu Zhang <zhangyoufu@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 3 insertions, 13 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 60c8ffe..eb51d47 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -8163,7 +8163,6 @@ static int
 describe_command(char *command, const char *path, int describe_command_verbose)
 {
 	struct cmdentry entry;
-	struct tblentry *cmdp;
 #if ENABLE_ASH_ALIAS
 	const struct alias *ap;
 #endif
@@ -8193,15 +8192,8 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 		goto out;
 	}
 #endif
-	/* Then check if it is a tracked alias */
-	cmdp = cmdlookup(command, 0);
-	if (cmdp != NULL) {
-		entry.cmdtype = cmdp->cmdtype;
-		entry.u = cmdp->param;
-	} else {
-		/* Finally use brute force */
-		find_command(command, &entry, DO_ABS, path);
-	}
+	/* Brute force */
+	find_command(command, &entry, DO_ABS, path);
 
 	switch (entry.cmdtype) {
 	case CMDNORMAL: {
@@ -8216,9 +8208,7 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 			} while (--j >= 0);
 		}
 		if (describe_command_verbose) {
-			out1fmt(" is%s %s",
-				(cmdp ? " a tracked alias for" : nullstr), p
-			);
+			out1fmt(" is %s", p);
 		} else {
 			out1str(p);
 		}