linux-kernel - [PATCH] coredump: prevent double-free on an error path in core dumper

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Date:	Wed, 12 Sep 2012 13:37:25 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roland McGrath <roland@...k.frob.com>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>
Subject: [PATCH] coredump: prevent double-free on an error path in core dumper

In !CORE_DUMP_USE_REGSET case, if elf_note_info_init fails to allocate memory
for info->fields, it frees already allocated stuff and returns
error to its caller, fill_note_info. Which in turn returns
error to its caller, elf_core_dump. Which jumps to cleanup
label and calls free_note_info, which will happily try to
free all info->fields again. BOOM.

This is the fix.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Denys Vlasenko <vda.linux@...glemail.com>
---
 fs/binfmt_elf.c |   19 ++++---------------
 1 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 760d7f5..1b4efbc 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1695,30 +1695,19 @@ static int elf_note_info_init(struct elf_note_info *info)
 		return 0;
 	info->psinfo = kmalloc(sizeof(*info->psinfo), GFP_KERNEL);
 	if (!info->psinfo)
-		goto notes_free;
+		return 0;
 	info->prstatus = kmalloc(sizeof(*info->prstatus), GFP_KERNEL);
 	if (!info->prstatus)
-		goto psinfo_free;
+		return 0;
 	info->fpu = kmalloc(sizeof(*info->fpu), GFP_KERNEL);
 	if (!info->fpu)
-		goto prstatus_free;
+		return 0;
 #ifdef ELF_CORE_COPY_XFPREGS
 	info->xfpu = kmalloc(sizeof(*info->xfpu), GFP_KERNEL);
 	if (!info->xfpu)
-		goto fpu_free;
+		return 0;
 #endif
 	return 1;
-#ifdef ELF_CORE_COPY_XFPREGS
- fpu_free:
-	kfree(info->fpu);
-#endif
- prstatus_free:
-	kfree(info->prstatus);
- psinfo_free:
-	kfree(info->psinfo);
- notes_free:
-	kfree(info->notes);
-	return 0;
 }
 
 static int fill_note_info(struct elfhdr *elf, int phdrs,
-- 
1.7.7.6

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