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authorAndy Lutomirski <luto@amacapital.net>2014-12-17 14:48:30 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-08 09:58:15 -0800
commitd011d586b3f9f1b08f3deb080d8542f56963dc28 (patch)
tree822c4c9f9496620844d252b97e1e2eb808748a8d /fs
parent81f250e1cf8048e4780e46d5219b0e7f943a336b (diff)
downloadlinux-linaro-stable-d011d586b3f9f1b08f3deb080d8542f56963dc28.tar.gz
x86/tls: Don't validate lm in set_thread_area() after all
commit 3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0 upstream. It turns out that there's a lurking ABI issue. GCC, when compiling this in a 32-bit program: struct user_desc desc = { .entry_number = idx, .base_addr = base, .limit = 0xfffff, .seg_32bit = 1, .contents = 0, /* Data, grow-up */ .read_exec_only = 0, .limit_in_pages = 1, .seg_not_present = 0, .useable = 0, }; will leave .lm uninitialized. This means that anything in the kernel that reads user_desc.lm for 32-bit tasks is unreliable. Revert the .lm check in set_thread_area(). The value never did anything in the first place. Fixes: 0e58af4e1d21 ("x86/tls: Disallow unusual TLS segments") Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/d7875b60e28c512f6a6fc0baf5714d58e7eaadbb.1418856405.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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