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kernel/sys.c: fix potential Spectre v1 issue
commit 23d6aef74d
upstream.
`resource' can be controlled by user-space, hence leading to a potential
exploitation of the Spectre variant 1 vulnerability.
This issue was detected with the help of Smatch:
kernel/sys.c:1474 __do_compat_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap)
kernel/sys.c:1455 __do_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap)
Fix this by sanitizing *resource* before using it to index
current->signal->rlim
Notice that given that speculation windows are large, the policy is to
kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].
[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2
Link: http://lkml.kernel.org/r/20180515030038.GA11822@embeddedor.com
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 2 additions and 0 deletions
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@ -1395,6 +1395,7 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
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if (resource >= RLIM_NLIMITS)
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return -EINVAL;
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resource = array_index_nospec(resource, RLIM_NLIMITS);
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task_lock(current->group_leader);
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x = current->signal->rlim[resource];
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task_unlock(current->group_leader);
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@ -1414,6 +1415,7 @@ COMPAT_SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
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if (resource >= RLIM_NLIMITS)
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return -EINVAL;
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resource = array_index_nospec(resource, RLIM_NLIMITS);
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task_lock(current->group_leader);
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r = current->signal->rlim[resource];
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task_unlock(current->group_leader);
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