[28/38] exec: do not call request_module() twice from search_binary_handler()

[Greg KH]

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

commit 912193521b719fbfc2f16776febf5232fe8ba261 upstream.

Currently, search_binary_handler() tries to load binary loader module
using request_module() if a loader for the requested program is not yet
loaded.  But second attempt of request_module() does not affect the result
of search_binary_handler().

If request_module() triggered recursion, calling request_module() twice
causes 2 to the power of MAX_KMOD_CONCURRENT (= 50) repetitions.  It is
not an infinite loop but is sufficient for users to consider as a hang up.

Therefore, this patch changes not to call request_module() twice, making 1
to the power of MAX_KMOD_CONCURRENT repetitions in case of recursion.

Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-by: Richard Weinberger <richard@xxxxxx>
Tested-by: Richard Weinberger <richard@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Maxim Uvarov <muvarov@xxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

---
 fs/exec.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1411,6 +1411,8 @@ int search_binary_handler(struct linux_b
 			    printable(bprm->buf[2]) &&
 			    printable(bprm->buf[3]))
 				break; /* -ENOEXEC */
+			if (try)
+				break; /* -ENOEXEC */
 			request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
 #endif
 		}


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