[34-longterm 134/179] xtensa: prevent arbitrary read in ptrace

From: Paul Gortmaker
Date: Mon May 14 2012 - 22:38:43 EST

From: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 0d0138ebe24b94065580bd2601f8bb7eb6152f56 upstream.

Prevent an arbitrary kernel read. Check the user pointer with access_ok()
before copying data in.

[akpm@xxxxxxxxxxxxxxxxxxxx: s/EIO/EFAULT/]
Signed-off-by: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>
Cc: Christian Zankel <chris@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
arch/xtensa/kernel/ptrace.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index 9d4e1ce..f0ccfc7 100644
--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -147,6 +147,9 @@ int ptrace_setxregs(struct task_struct *child, void __user *uregs)
elf_xtregs_t *xtregs = uregs;
int ret = 0;

+ if (!access_ok(VERIFY_READ, uregs, sizeof(elf_xtregs_t)))
+ return -EFAULT;
/* Flush all coprocessors before we overwrite them. */

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