[git commit] grep: skip grepping symlinks to directories

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=6bcc2c0f6cb868232ec06231aa37a3fa65c59d22
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

When grep is passed -r, recursive_action will treat any symlinks to
directories not in the root as normal files, since it lstat's them and
is therefore told they are not directories. However, file_action_grep
will still try to fopen and read from them to see whether they match,
which varies in behaviour across platforms. Linux will give EISDIR and
thus grep will not find any matching lines, but FreeBSD will give the
raw contents of the directory itself, which may match the given pattern.
Also, if grep is passed -c, it will even print a count for these
symlinks, even on Linux.

Since this recursive_action behaviour is required for the correct
functioning of other applets, such as tar, grep should handle this
special case and skip any such symlinks.

function                                             old     new   delta
file_action_grep                                      80     161     +81

Signed-off-by: James Clarke <jrtc27 at jrtc27.com>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 findutils/grep.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/findutils/grep.c b/findutils/grep.c
index f72175a..fc6de4b 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -639,11 +639,28 @@ static void load_regexes_from_file(llist_t *fopt)
 }
 
 static int FAST_FUNC file_action_grep(const char *filename,
-			struct stat *statbuf UNUSED_PARAM,
+			struct stat *statbuf,
 			void* matched,
 			int depth UNUSED_PARAM)
 {
-	FILE *file = fopen_for_read(filename);
+	FILE *file;
+
+	/* If we are given a link to a directory, we should bail out now, rather
+	 * than trying to open the "file" and hoping getline gives us nothing,
+	 * since that is not portable across operating systems (FreeBSD for
+	 * example will return the raw directory contents). */
+	if (S_ISLNK(statbuf->st_mode)) {
+		struct stat sb;
+		if (stat(filename, &sb) != 0) {
+			if (!SUPPRESS_ERR_MSGS)
+				bb_simple_perror_msg(filename);
+			return 0;
+		}
+		if (S_ISDIR(sb.st_mode))
+			return 1;
+	}
+
+	file = fopen_for_read(filename);
 	if (file == NULL) {
 		if (!SUPPRESS_ERR_MSGS)
 			bb_simple_perror_msg(filename);