6.6-stable review patch. If anyone has any objections, please let me know.
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From: Mark Rutland mark.rutland@arm.com
commit ca62d90085f4af36de745883faab9f8a7cbb45d3 upstream.
Currently tagged_addr_ctrl_set() doesn't initialize the temporary 'ctrl' variable, and a SETREGSET call with a length of zero will leave this uninitialized. Consequently tagged_addr_ctrl_set() will consume an arbitrary value, potentially leaking up to 64 bits of memory from the kernel stack. The read is limited to a specific slot on the stack, and the issue does not provide a write mechanism.
As set_tagged_addr_ctrl() only accepts values where bits [63:4] zero and rejects other values, a partial SETREGSET attempt will randomly succeed or fail depending on the value of the uninitialized value, and the exposure is significantly limited.
Fix this by initializing the temporary value before copying the regset from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG, NT_ARM_SYSTEM_CALL). In the case of a zero-length write, the existing value of the tagged address ctrl will be retained.
The NT_ARM_TAGGED_ADDR_CTRL regset is only visible in the user_aarch64_view used by a native AArch64 task to manipulate another native AArch64 task. As get_tagged_addr_ctrl() only returns an error value when called for a compat task, tagged_addr_ctrl_get() and tagged_addr_ctrl_set() should never observe an error value from get_tagged_addr_ctrl(). Add a WARN_ON_ONCE() to both to indicate that such an error would be unexpected, and error handlnig is not missing in either case.
Fixes: 2200aa7154cb ("arm64: mte: ptrace: Add NT_ARM_TAGGED_ADDR_CTRL regset") Cc: stable@vger.kernel.org # 5.10.x Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Will Deacon will@kernel.org Reviewed-by: Mark Brown broonie@kernel.org Link: https://lore.kernel.org/r/20241205121655.1824269-2-mark.rutland@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/ptrace.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -1385,7 +1385,7 @@ static int tagged_addr_ctrl_get(struct t { long ctrl = get_tagged_addr_ctrl(target);
- if (IS_ERR_VALUE(ctrl)) + if (WARN_ON_ONCE(IS_ERR_VALUE(ctrl))) return ctrl;
return membuf_write(&to, &ctrl, sizeof(ctrl)); @@ -1399,6 +1399,10 @@ static int tagged_addr_ctrl_set(struct t int ret; long ctrl;
+ ctrl = get_tagged_addr_ctrl(target); + if (WARN_ON_ONCE(IS_ERR_VALUE(ctrl))) + return ctrl; + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl, 0, -1); if (ret) return ret;