linux-kernel - Re: [PATCH 7/7] modpost: handle relocations mismatch in __ex

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Date:	Mon, 13 Apr 2015 20:48:56 +0930
From:	Rusty Russell <rusty@...abs.org>
To:	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	Oleg Nesterov <oleg@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: Re: [PATCH 7/7] modpost: handle relocations mismatch in __ex_table.

Quentin Casasnovas <quentin.casasnovas@...cle.com> writes:
> __ex_table is a simple table section where each entry is a pair of
> addresses - the first address is an address which can fault in kernel
> space, and the second address points to where the kernel should jump to
> when handling that fault.  This is how copy_from_user() does not crash the
> kernel if userspace gives a borked pointer for example.

Warnings on 32-bit:

scripts/mod/modpost.c:1562:7: warning: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 4 has type ‘Elf32_Addr’ [-Wformat=]
       to_pretty_name, tosec, tosym_name, to_pretty_name_p);
       ^
scripts/mod/modpost.c:1574:4: warning: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 4 has type ‘Elf32_Addr’ [-Wformat=]
    fromsec, r->r_offset, tosec, tosec, tosec);
    ^
scripts/mod/modpost.c: In function ‘extable_mismatch_handler’:
scripts/mod/modpost.c:1596:9: warning: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 3 has type ‘Elf32_Addr’ [-Wformat=]
         fromsec, r->r_offset, tosec, modname);
         ^
scripts/mod/modpost.c:1604:10: warning: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 3 has type ‘Elf32_Addr’ [-Wformat=]
          fromsec, r->r_offset, tosec);
          ^
scripts/mod/modpost.c:1611:10: warning: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 3 has type ‘Elf32_Addr’ [-Wformat=]
          fromsec, r->r_offset, tosec);
          ^

Fixed like so:

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 7b56ae567fba..b495547e321f 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1557,7 +1557,7 @@ static void report_extable_warnings(const char* modname, struct elf_info* elf,
 
 	warn("%s(%s+0x%lx): Section mismatch in reference"
 	     " from the %s %s%s to the %s %s:%s%s\n",
-	     modname, fromsec, r->r_offset, from_pretty_name,
+	     modname, fromsec, (long)r->r_offset, from_pretty_name,
 	     fromsym_name, from_pretty_name_p,
 	     to_pretty_name, tosec, tosym_name, to_pretty_name_p);
 
@@ -1571,7 +1571,7 @@ static void report_extable_warnings(const char* modname, struct elf_info* elf,
 			"list of authorized sections to jump to on fault.\n"
 			"This can be achieved by adding \"%s\" to \n"
 			"OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.\n",
-			fromsec, r->r_offset, tosec, tosec, tosec);
+			fromsec, (long)r->r_offset, tosec, tosec, tosec);
 }
 
 static void extable_mismatch_handler(const char* modname, struct elf_info *elf,
@@ -1593,7 +1593,7 @@ static void extable_mismatch_handler(const char* modname, struct elf_info *elf,
 		      "Something is seriously wrong and should be fixed.\n"
 		      "You might get more information about where this is\n"
 		      "coming from by using scripts/check_extable.sh %s\n",
-		      fromsec, r->r_offset, tosec, modname);
+		      fromsec, (long)r->r_offset, tosec, modname);
 	else if (!is_executable_section(elf, get_secindex(elf, sym))) {
 		if (is_extable_fault_address(r))
 			fatal("The relocation at %s+0x%lx references\n"
@@ -1601,14 +1601,14 @@ static void extable_mismatch_handler(const char* modname, struct elf_info *elf,
 			      "it is not possible for the kernel to fault\n"
 			      "at that address.  Something is seriously wrong\n"
 			      "and should be fixed.\n",
-			      fromsec, r->r_offset, tosec);
+			      fromsec, (long)r->r_offset, tosec);
 		else
 			fatal("The relocation at %s+0x%lx references\n"
 			      "section \"%s\" which is not executable, IOW\n"
 			      "the kernel will fault if it ever tries to\n"
 			      "jump to it.  Something is seriously wrong\n"
 			      "and should be fixed.\n",
-			      fromsec, r->r_offset, tosec);
+			      fromsec, (long)r->r_offset, tosec);
 	}
 }
 


Thanks,
Rusty.
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